To address the privacy leakage problem caused by the model parameters memorizing some features of the data during the training process of the Convolutional Neural Network （CNN） models， a Gradient Descent with Momentum algorithm based on Differential Privacy in CNN （DPGDM） was proposed. Firstly， the Gaussian noise meeting differential privacy was added to the gradient in the backpropagation process of model optimization， and the noise-added gradient value was used to participate in the model parameter update process， so as to achieve differential privacy protection for the overall model. Secondly， to reduce the impact of the introduction of differential privacy noise on convergence speed of the model， a learning rate decay strategy was designed and then the gradient descent with momentum algorithm was improved. Finally， to reduce the influence of noise on the accuracy of the model， the value of the noise scale was adjusted dynamically during model optimization， thereby changing the amount of noise that needs to be added to the gradient in each round of iteration. Experimental results show that compared with DP-SGD （Differentially Private Stochastic Gradient Descent） algorithm， the proposed algorithm can improve the accuracy of the model by about 5 and 4 percentage points at privacy budget of 0.3 and 0.5， respectively， proving that by using the proposed algorithm， the model usability is improved and privacy protection of the model is achieved.
