This paper proposes an adaptive intermittent crawl gait for quadruped robots to walk on a slope. In the proposed method, the inclination of a floor is estimated in real time by the displacement of the projection of the center of gravity from the nominal position. Depending upon the estimated inclination, the gait is changed in order to gain the longitudinal stability margin. Experiments and dynamic simulations are performed to validate the proposed method. The results are presented and discussed.