A new image reconstruction method for oilair lubrication testing ECT system based on OTSU was proposed.This algorithm was based on the Landweber iterative algorithm,the gas phase in the oilair lubrication was taken as the background and the liquid phase was used as the target,and the OTSU method was used to obtain the gray threshold that the misclassification rate of gas and liquid phase is the minimum.The oil film thickness measurement method based on image graylevel was developed.Simulation results show that compared with linear back projection(LBP) algorithm and Landweber algorithm,the algorithm based on OTSU can eliminate effectively the artifacts in the LBP and Landweber algorithms to get clear oilair boundaries and accurate oil film thickness.The algorithm is also simple and has a high imaging precision.