The rapid development of the Internet and e-commerce has made the web a public platform for people to communicate and exchange ideas. Consumers have generated a large number of online reviews based on online platforms, which has a wide impact and attracts the active attention of experts and scholars. Research on sentiment analysis based on online reviews has also been evolving. This paper focuses on sentiment analysis methods based on online reviews and their applications. It presents an overview of the above content. Besides, possible research directions and contents in the future are pointed out by analyzing the existing research problems.