Abstract: A rear suspension system for a bicycle which includes a front part having a top tube, a down tube and a seat bracket, and a rear part has seat stays and chain stays. The seat tube has a frame located close to the bottom bracket. A top link unit is pivotably connected to the seat stays and extends toward the front part to form a first pivotal portion. The chain stays are connected to a down link unit which extends into the frame. A second pivotal portion is formed at the mediate portion of the down link unit. A shock-absorbing device has its top end pivotably connected to the first pivotal portion and the lower end of the shock-absorbing device extends into the frame and is pivotably connected to the second pivotal portion which is located close to the axis of the seat tube to provide stable buffering action.