Load sensing pumps have been widely used in diverse hydraulic systems. Studies show that structural parameters have undeniable impacts on the characteristics and efficiency of the load sensing pump. The main purpose of this article is to study the influence of load sensing pump structure parameters on flow characteristics. In the present study, a nonlinear multi-parameter model is proposed for this type of pump. In this model, different parameters, including spool clearance, spool covering amount, internal leakage are considered to reflect the displacement adjustment process of the load sensing pump. Moreover, a frequency sweep method is proposed to analyze the frequency domain of the nonlinear mathematical model. An experiment rig was built to study the influence of key structural parameters on the dynamic follow-up characteristics of the pump flow. The obtained results show that the diameter of the orifice d can significantly affect the working characteristics of the pump. It is found that a large diameter of the orifice d can improve the phase following ability of the system, while a small diameter of the orifice d can reduce the bypass flow rate and increase the amplitude following ability. This paper provides a new consideration to study the dynamic follow-up characteristics of the load sensing pump.