As legged robots are suitable to be used in unstructured environments, it becomes a popular field of research nowadays. In this paper, the development of quadruped robots is summarized. And several typical and recent robot systems are addressed in details, such as HyQ series, StarlETH, ANYmal, MIT Cheetah and BigDog, etc. Furthermore, some key techniques of environment perception for quadruped robots, including sensors, feature extraction and identification, mapping and SLAM, are also discussed. Finally, future researches of quadruped robots in environment perception are given.