The invention provides a ratchet clamp, comprising a first clamp arm, a second clamp arm and a ratchet mechanism provided between the first clamp arm and the second clamp arm. An elastic member is arranged between the ratchet mechanism and the second clamp arm. The ratchet mechanism includes a toothed bar, a pivoting member. The pivoting member includes a toothed piece, a housing and a lever. During clamping, the pivoting member pivots in whole within a certain range under the effect of the elastic member, and the toothed bar and toothed piece are engaged by undercut, maintaining the clamping force, and the elastic member protects the engagement between the toothed bar and the toothed piece from sliding apart. When opened, the interference fit between the toothed bar and the toothed piece enable the user to use small force pulling the lever to disengage the toothed piece, and also prevent accidental unloading force from opening the ratchet mechanism. The self lock state of the ratchet clamp of the invention is very safe and stable, the maximum clamping force at the jaw opening portion can reach about 50 Kg, and 85% of the maximum clamping force can be maintained after the user releases the clamp arms.