Shock absorber for a bicycle

A shock absorber, the shock-absorbing function of which can be enabled/disabled during movement and includes a basement (10), a clutch assembly (A), a control assembly (B) and a shock-absorbing spring (11), the shock-absorbing spring (11) provides damper elastic force for the respective components of the shock absorber. The shock-absorbing function can be disenabled when riding up a slope, so as to prevent the drag force being increased by the up and down motion of the shock absorber. The shock-absorbing function can be enabled when riding on a horizontal road, and it can be disenabled again when riding down a slope, so as to prevent the increase of the front tilt angle of the bike and leading to turnover.