In recent years, several countries, such as China and the United States, and high-tech companies, such as Google, have increased investment in artificial intelligence. Deep learning is one of the current artificial intelligence research key areas. We analyze and summarize the latest progress and future research directions of deep learning. First, we outline three basic models of deep learning, which are multilayer perceptrons, convolutional neural networks, and recurrent neural networks. On this basis, we further analyze the emerging new models of convolution neural networks and recurrent neural networks. Furthermore, we summarize the applications of deep learning in many areas of artificial intelligence, including speech processing, computer vision, and natural language processing. Finally, we discuss the existing problems of deep learning and provide the corresponding possible solutions.