The leg mechanism of the quadruped robot comprises a trunk and legs, the trunk is a rectangular frame; the four legs are symmetrically installed on the two sides of the front end and the two sides ofthe rear end of the trunk in pairs. Each leg comprises a connecting rod A, a connecting rod B, a connecting rod C, a connecting rod D, a driving motor A and a driving motor B; the driving motor A andthe driving motor B are fixedly mounted on the side edge of the trunk; the two are positioned at the same horizontal height; the connecting rod A, the connecting rod B, the connecting rod C and the connecting rod D are sequentially hinged to form a planar five-connecting-rod mechanism; wherein the connecting rod A is connected with a crankshaft of the driving motor A and swings under the driving of the driving motor A so as to drive the planar five-connecting-rod mechanism to deform, and the connecting rod B is connected with a crankshaft of the driving motor B and swings under the driving ofthe driving motor B so as to drive the planar five-connecting-rod mechanism to deform. The quadruped robot has the advantages that the leg structure is relatively simple, stable and reliable, and themoving functions of advancing, retreating, turning, turning around in situ and the like of the quadruped robot can be achieved.