The proportion sliding mode strategy retains the linear control advantages, but the presence of buffeting will reduce the control precision, even stimulate the system unmodeled dynamics or cause mechanical resonance. These deficiencies seriously restrict the application of the proportion of sliding mode control in electrohydraulic position system. In order to avoid chattering influence on the system accuracy and stability, self-tuning sliding mode switching gain is designed to soften the control signal, according to the switch function and its derivative of the fuzzy model. The results show that the system achieves the gain self-adjusting by fuzzy theory, reduces the buffeting, implements high-precision control, and retains characteristics both of the anti-parameter perturbations and anti-disturbance ability