The paper analyses the investigation of father and the displacement in fact, discusses the distribution of the lateral soilpressure in soilnailed wall qualitatively , then discusses the distribution and the magnitude of the active soilpressure in soilnailed wall in theory, in the end it brings forward an effective predigested mode of the lateral soilpressure in soilnailed, it supplies a forceful gist to optimize the design more of the soilnailed wall.