The invention provides a positioning clamp. The positioning clamp comprises a support, a left-and-right positioning mechanism, a front-and-back positioning mechanism and a worktable board, wherein thesupport supports the left-and-right positioning mechanism, the left-and-right positioning mechanism comprise a left-and-right installing bottom plate, a left positioning mechanism and a right positioning mechanism, wherein the left positioning mechanism comprises a driving air cylinder I, an air cylinder connecting block I, an air cylinder fixing block I, a left positioning base, a sliding wire rail, a line rail installing base I, a left torsion spring base, a torsion spring installing base and a torsion spring positioning block; the right positioning mechanism comprises a driving air cylinder II, an air cylinder connecting block II, an air cylinder fixing block II, a right positioning base, a sliding wire rail, a line rail installing base II, a right base and a right positioning block; the front-and-right positioning mechanism comprises a front positioning mechanism and a back positioning mechanism, wherein the front positioning mechanism comprises a front positioning base, a front installing base and a front positioning block; and the back positioning mechanism comprises a bottom plate cushion block, an adsorbing table base, an adsorbing table, an air cylinder installing base, adriving air cylinder III, an installing base and a back positioning block. According to the clamp, centring can be achieved, a plurality of workpieces can be positioned at the same time and the clampdoes not greatly occupy the worktable board.