Deep learning has developed rapidly in recent years,attracting the attention of numerous re-searchers.Since a wide range of topics are covered in this field,we are wondering what topics researchers have concerned about.However,after investigation,we find that very few researchers have paid attention to this demand.In this paper,we conduct a large-scale study to analyze the questions faced by deep learning developers.We use Stack Overflow,one of the largest question&answer sites,as our data source,and extract 32969 posts about deep learning as our studied dataset.After filtering,augmenting and pre-processing the post datasets from Stack Overflow,we use the latent Dirichlet allocation (LDA) topic model to summarize 30 topics based on their text content.In addition,we measure the difficulty and popularity of each topic,compare the different issues faced by different deep learning frameworks,and analyze the development trend of each topic.Our main results are as follows:(1) developers ask a broad spectrum of questions about deep-learning,ranging from Data Shape to Object Detection;(2) Gradient Propagation is the most popular among all the topics and (3) Object Detection is the most difficult;(4) issues of Package Installation,Code Understanding and Method Introduction are common in the current different deep learning frameworks;(5) there are three trends in these topics,e.g.,a significant rising trend is found in the number of discussion on Data Shape.Finally,based on our research findings,we make some targeted and valuable suggestions for developers,researchers,educators,and framework providers of deep learning.