Abstract: An advanced hydraulic quadruped robot named SCalf is introduced, and its mechanism, onboard power system, hydraulic actuators and real-time control system are presented. By using a locomotion control based on attitude decoupling, SCalf can move fast and stably. SCalf is also able to adapt to complex terrains based on a leg compliant control system with contact force sensors on its feet. Numerous experiments show that SCalf can safely walk through various complex terrains including rough terrain, slippery terrain, slope and stairs. The self-balancing of SCalf under side impact has also been experimentally verified. All these results demonstrate the walking ability of SCalf on complex terrains.