The invention discloses a damage detection device for a cylindrical pipeline outside a valve, and the detection device comprises a support frame, two rotating motors, rotating mechanical arms, a clamping mechanism and a detecting mechanism, wherein the rotating motors are installed on the support frame at intervals, the output ends of the rotating motors are installed with the rotating mechanicalarms, the clamping mechanism is installed above the rotating mechanical arms, and the detecting mechanism is installed above the clamping mechanism. The damage detection device provided by the invention solves the technical problem of inconvenient valve pipeline detection in the prior art.