Abstract: The pintle controlled solid rocket motor shows distinct non-steady characteristic when nozzle aera is changed by pintle motion. In order to understand the non-steady characteristic, simulation of inflow field during the thrust controlling process with pintle motion was implemented by using the unique dynamic mesh layering model in Fluent software. Velocity of pintle move, nozzle geometry and propellant parameter were investigated as the main influence factors on the non-steady characteristic. It is found that the velocity and pressure index affect the non-steady characteristic greatly, the effect of nozzle convergence half angle on the non-steady characteristic takes the second and expansion half angle and pintle radius have almost no affect to the non-steady characteristic.