Abstract: In view of the insufficiency of the motion range and output force of the pneumatic muscle (PM) joint driven by one group of antagonistic PMs, a humanoid elbow driven by cascaded PMs is proposed. The elbow joint is driven by two groups of antagonistic PMs. The model of the humanoid elbow joint is established, and a fuzzy controller is designed, in which the joint flexibility C and angle are taken as input, and upper and lower arm ratio K and PI (proportional-integral) parameters are taken as output. The PI control and fuzzy PI control are used to perform the elbow joint tracking experiment respectively. The experiments show that the cascaded joint design is rational and the fuzzy control method is effective.