Previously, two-wheel wheelchair systems have been receiving attention since they have high mobility better than conventional four-wheel wheelchair Systems. However, two-wheel wheelchair must achieve stabilization control under disturbance caused by modeling error or road situation since two-wheel wheelchair systems are underactuated systems such as inverted pendulum. In this research, step passage motion in two-wheel wheelchair systems is considered. Synthesized Pitch Angle Disturbance Observer (SPADO) is utilized to compensate pitch angle disturbance and wheel angle disturbance. Reaction Torque Observer (RTOB) is conducted to estimate pure external wheel disturbance. Furthermore, variable repulsive compliance control is conducted to determine the optimal pitch angle command for whole step passage motion.