Abstract: The paper deduces dynamic equation of hydraulic driving system under impact load and simulated the response of control rod.Results show that the mechanism for response of hydraulic driving system under dissimilar impact load is different.When the impact is fast,since the hydraulic driving system did not have time to adjust,the response amplitude of control rod mainly depends on the input displacement of impact load and increases as the input displacement increases.The response amplitude also relates to the impact direction.When the reactor moved down rapidly,the response displacement of the control rod is larger.When the impact is slow,the response amplitude is very small if the impact acceleration is not higher.