Abstract: Spring loaded inverted pendulum (SLIP) based equivalent leg is an important gait analyzing model in the realm of mobile robot. Due to superb load capacity and dynamic performance, hydraulic based robot has gained more popularity. As an equivalent model for articulated leg in hydraulic legged robot, hydraulic activated SLIP model shows its importance in hydraulic robot gait analysis. In this paper, analyzing the hydraulic actuated 1-DOF SLIP model, an active compliance based hopping method was proposed. And the separation control for stance phase compression and decompression stage was conducted. System parameters were analyzed with simulation for hopping performance and hopping experiments verified the effectiveness of impact force reduction and hopping height control performance.