Remote parameter control (RPC) is presently the major technique for road simulator. However, the iterative parameters settlement in traditional RPC method much relies on test-personnel's experience. To aim at it, this article presents an improved road simulation iterative method, with which stochastic pavement unevenness has been reproduced on a road simulation test rig. After figuring out input errors by tradition RPC, a smooth filter was devised and then next step input signal was computed by taking filtered error signal directly as the correction of input signal in the iterative formula. For the sake of iterative process stabilization, filter parameter was determined according to the value of iterative relative error. Test results indicate that the iterative process is steady and waveform reproducing precision is high by applying filtered error signal.