In order to solve the problem of insufficient mining of potential association between remote nodes in human action recognition tasks， and the problem of high training cost caused by using multi-modal data， a multi-scale feature fusion human action recognition method under the condition of single mode was proposed. Firstly， the global feature correlation of the original skeleton diagram of human body was carried out， and the coarse-scale global features were used to capture the connections between the remote nodes. Secondly， the global feature correlation graph was divided locally to obtain the Complementary Subgraphs with Global Features （CSGFs）， the fine-scale features were used to establish the strong correlation， and the multi-scale feature complementarity was formed. Finally， the CSGFs were input into the spatial-temporal Graph Convolutional module for feature extraction， and the extracted results were aggregated to output the final classification results. Experimental results show that the accuracy of the proposed method on the authoritative action recognition dataset NTU RGB+D60 is 89.0% （X-sub） and 94.2% （X-view） respectively. On the challenging large-scale dataset NTU RGB+D120， the accuracy of the proposed method is 83.3% （X-sub） and 85.0% （X-setup） respectively， which is 1.4 and 0.9 percentage points higher than that of the ST-TR （Spatial-Temporal TRansformer） under single modal respectively， and 4.1 and 3.5 percentage points higher than that of the lightweight SGN （Semantics-Guided Network）. It can be seen that the proposed method can fully exploit the synergistic complementarity of multi-scale features， and effectively improve the recognition accuracy and training efficiency of the model under the condition of single modal.

In order to solve the problem of huge labeling cost for person re-identification， a method of one-shot video-based person re-identification with multi-loss learning and joint metric was proposed. Aiming at the problem that the number of label samples is small and the model obtained is not robust enough， a Multi-Loss Learning （MLL） strategy was proposed. In each training process， different loss functions were used for different data to optimize and improve the discriminative ability of the model. Secondly， a Joint Distance Metric （JDM） was proposed for label estimation， which combined the sample distance and the nearest neighbor distance to further improve the accuracy of pseudo label prediction. JDM solved the problems of the low accuracy of label estimation for unlabeled data， and the instability in the training process caused by the unlabeled data not fully utilized. Experimental results show that compared with the one-shot progressive learning method PL （Progressive Learning）， the rank-1 accuracy reaches 65.5% and 76.2% on MARS and DukeMTMC-VideoReID datasets when the ratio of pseudo label samples added per iteration is 0.10， with the improvement of the proposed method of 7.6 and 5.2 percentage points， respectively.

Current research on Person Re-Identification （Re-ID） mainly concentrates on short-term situations with person’s clothing usually unchanged. However， more common practical cases are long-term situations， in which a person has higher possibility to change his clothes， which should be considered by Re-ID models. Therefore， a method of person re-identification with cloth changing based on joint loss capsule network was proposed. The proposed method was based on ReIDCaps， a capsule network for cloth-changing person re-identification. In the method， vector-neuron capsules that contain more information than traditional scalar neurons were used. The length of the vector-neuron capsule was used to represent the identity information of the person， and the direction of the capsule was used to represent the clothing information of the person. Soft Embedding Attention （SEA） was used to avoid the model over-fitting. Feature Sparse Representation （FSR） mechanism was adopted to extract discriminative features. The joint loss of label smoothing regularization cross-entropy loss and Circle Loss was added to improve the generalization ability and robustness of the model. Experimental results on three datasets including Celeb-reID， Celeb-reID-light and NKUP prove that the proposed method has certain advantages compared with the existing person re-identification methods.