The invention discloses a two-leg robot leg mechanism based on driving of artificial muscles. The two-leg robot leg mechanism comprises a single-shaft hip joint, thigh rods, a pneumatic artificial muscle driving mechanism, bionic knee joints, crus rods, ankle joint transmission mechanisms and artificial flexible feet, wherein the single-shaft hip joint is connected with the thigh rods, the thigh rods are connected with the bionic knee joints, the bionic knee joints, the crus rods, the ankle joint transmission mechanisms and the artificial flexible feet are sequentially connected, the pneumatic artificial muscle driving mechanism comprises a transverse rod, the transverse rod is perpendicularly fixed in the thigh rods, two pneumatic artificial muscles are arranged in parallel, one ends of the two pneumatic artificial muscles are fixedly connected with the transverse rod, the other ends of the two pneumatic artificial muscles are connected to each other through a chain, the chain is connected with a driving shaft of the bionic knee joints through a chain wheel, and driving is achieved through opposite pulling of the pair of pneumatic muscles. The two-leg robot leg mechanism has the advantages of being natural in walking gait, high in adaptability to road conditions, small in motion impact, high in walking speed, small in energy consumption, capable of achieving flexible motion of joints, simple in structure and delicate in design.