The study of quadruped robots is an important branch of robotics. As is known to all, quadruped robots can go through the rough terrain easily and they are useful in field operation. Whether quadruped robot can interact softly with the environment is an important index to value its property. This paper presents the preliminary research of a quadruped robot, mainly focus on the mechanical design and corresponding configurations. A new kind of elastic joint is designed to improve the flexibility of the robot to adapt to the environment. This elastic joint has a widely portability and it can be used in many occasions where elastic actuators are needed. The dynamics and control of the elastic module are analyzed. The simulation results are also shown at the end of the paper to demonstrate the effectiveness of the elastic module.