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When sprayer works in the field, boom movement seriously affected the spray distribution, suspension system is the key device to control the dynamic behavior of boom. The response of a boom suspension should be such that it isolates the boom from high frequency roll of vehicle as it travels over bumpy ground, while transmitting low frequency roll so that the boom can follow undulating and sloping ground. In order to solve the dynamics and control problems of double pendulum active and passive suspension mechanism, considering the coupling effect of vehicle body motion, change of terrain slope, friction of moving pair, etc., a higher order differential equation group was established to describe the dynamic behavior of boom by using the second kinds of Lagrange dynamics equation. Based on this, the dynamic characteristics of the passive suspension were studied, and the effects of these factors, such as damping, friction and pendulum length on the response characteristics were analyzed. A Matlab/Simulink simulation model of active suspension based on hydraulic proportional control was established, and then the influence of gain coefficient, time constant and suspension structure parameters on the boom response and tracking error was revealed. By using Stewart six degree of freedom motion simulation platform and dynamic testing system, step response test and frequency response test were conducted on a spray boom with pendulum suspension, the root mean square error between frequency response test value and the mathematical model predictive value was 0.087. It was demonstrated that the model could be used in the design of a suspension to give a specified response to the rolling motion of the spray vehicle，and the results showed that the model can be used to predict the dynamic response characteristics of the boom, and guide the design of large boom suspension.