Magnetic flux leakage detection technology is a common detection method in the field of pipeline internal detection. The analysis base on magnetic flux leakage signal is of great significance for pipeline safety evaluation. Establishing a two-dimensional simulation model of magnetic flux leakage detection, and studying the influence of excitation intensity on magnetic flux leakage signal in magnetic flux leakage detection; Based on the physical model of the influence of magnetization state on MFL signal, the excitation intensity is divided into three stages, namely, initial growth stage, nonlinear growth stage and saturated linear growth stage. The results show that the dividing points of the three stages is only affected by the depth of defects, and the simulation results are in good agreement with the physical model. The divided three stages effectively measure the influence of excitation intensity in pipeline magnetic flux leakage detection, which has guiding significance for magnetic flux leakage signal acquisition and analysis.