Rail is the infrastructure of railway traffic, and magnetic leakage technology is commonly used to detect the surface defects of ferromagnetic materials such as rail. For the problem of the leakage magnetic detection signal, a correlation-based filtering algorithm is proposed. The detection data is segmented according to the damage size, inspection speed and sampling speed, and then the amplitude of the lift-off interference is determined by comparing the correlation of the sampling data of the adjacent magnetic sensitivity sensor x direction and the relative size of the sampling data of each magnetic sensitivity sensor x and z direction. The experimental system is constructed to detect the artificial and natural defects of the rail surface, and the experimental results show that the proposed algorithm can effectively inhibit the lift-off method.,the SNR gain is above 1.7.