Fault tolerance is an important characteristic of quadruped robots. Actuator failure mode is the basis for research of fault tolerance and motion planning of quadruped robots. In this paper, the combination of actuator failures and the remained end-effector characteristics are investigated based on “GF sets” theory. With intersection operation property in “GF sets,” the remained motion ability can be easily judged. The combination of one and two actuator failures is analyzed in detail and some examples are used to illustrate the method of motion ability analysis. Experiments are carried out on the prototype of a novel quadruped robot and the results show that this method is effective for analysis of fault tolerance of quadruped robots.