Pseudo-label generation emerges as an effective strategy in semi-supervised stance detection. In practical applications, variations are observed in the quality of generated pseudo-labels. However, in the existing working, the quality of these labels is regarded as equivalent. Furthermore, the influence of category imbalance on the quality of pseudo-label generation is not fully considered. To address these issues, a Semi-supervised stance Detection model based on Category-aware curriculum Learning (SDCL) was proposed. Firstly, a pre-trained classification model was employed to generate pseudo-labels for unlabeled tweets. Then, tweets were sorted by category based on the quality of pseudo-labels, and the top k high-quality tweets for each category were selected. Finally, the selected tweets from each category were merged, re-sorted, and input into the classification model with pseudo-labels, thereby further optimizing the model parameters. Experimental results indicate that compared to the best-performing baseline model, SANDS (Stance Analysis via Network Distant Supervision), the proposed model demonstrates improvements in Mac-F1 (Macro-averaged F1) scores on StanceUS dataset by 2, 1, and 3 percentage points respectively under three different splits (with 500, 1 000, and 1 500 labeled tweets). Similarly, on StanceIN dataset, the proposed model exhibits enhancements in Mac-F1 scores by 1 percentage point under the three splits, thereby validating the effectiveness of the proposed model.