A clamping mechanism comprises: a main body; a pair of clamps are arranged on the main body, and each clamp may be moved along the clamping main body thereof the holding direction reciprocates relative to the main body; the clamping width maintaining mechanism is disposed on the main body for maintaining the clamping width of each pair of clamps to be adapted to the photographing device to be clamped; the adjusting mechanism is disposed on the main body for adjusting the spacing between one of each pair of clamps and the main body in the clamping direction for adjusting the clamping center of each pair of clamps while maintaining the clamping width of each pair of clamps relative to the center of the subject.