The utility model belongs to clamping mechanism technical field relates to a long workpiece clamping mechanism, including roof, both ends of roof bottom rotatoryly provided with rotary table, both ends of rotary table rotatoryly connect with clamping arm, the clamping arm is hinged with U -shaped seat, corresponding two U -shaped seats are provided with connecting plate, and both ends of connecting plate are hinged on two U -shaped seats respectively, the side of two connecting plates close to each other is fixedly connected with horizontal plate, the horizontal plate is provided with sliding channel, the inside sliding channel is slidably connected with sliding block, and the fixedly connected with reinforcing plate between two sliding blocks, wherein, reinforcing plate utilizes lifting control subassembly and moves up and down. The long workpiece clamping mechanism and device, through setting up clamping arm, horizontal plate and lifting control subassembly and so on structure, be applicable to columnar, V shape workpiece, and the rotary range of horizontal plate, rotary table is adjustable, be applicable to a variety of size V shape workpiece, improve the use efficiency of long workpiece clamping mechanism.