Frequency prediction after a disturbance is devoted to providing a decision-making foundation to power system emergency control. In practice, the quantity of utilized variables is limited by the dimensionality of the physical model. Meanwhile, the accuracy of cognitive results is affected by the modeling precision. Owing to the model simplification, the computation efficiency of model-driven methods is improved, but the accuracy is sacrificed. In this paper, a prediction model combining the improved system frequency response (ISFR) model and long short-term memory (LSTM) network is proposed to overcome this problem. Firstly, the ISFR model is employed to generate features representing system dynamic characteristics. Combined with the features provided by the ISFR model, the system operating features are applied to construct the training set for the deep learning network. Then, the LSTM network is introduced and trained to fit mapping relationship between multi-dimensional input features and system frequency response, thereby improving the overall accuracy of the integrated model. Finally, the simulation verification of the proposed model is performed in the IEEE 39-bus system and a realistic regional system. The simulation results demonstrate that the proposed model has better performance than that of traditional models.