A soft braking system was designed based on the mathematic model of wind turbine braking, and a semi-physical simulation test-bed for wind turbine was really formed. Analog simulation experiment for wind turbine soft braking was performed on the test-bed. Experiment results indicated that, when the wind turbine was regularly stopped, soft braking controls the high-speed switch valve on-off time by means of varying the PWM output of PLC, to adjust brake force through, which can make rotor speed fall down gently and minish the gearbox torque wave. 