In order to improve the frictional characteristics of automatic transmission fluid,a phosphorous boronized ashless dispersant was synthesized by using low molecular polyisobutylene maleic anhydride,polyene polyamine,boric acid and phosphide.The lowtemperature sludge dispersion property,hightemperature detergency,extreme pressure,antiwear,friction reducing and antishudder properties were evaluated and compared with the common ashless dispersants T151 and T161.Simulation evaluation and SAE No.2 test results show that the ashless dispersant synthesized not has good lowtemperature sludge dispersion property and excellent hightemperature detergency,extreme pressure,antiwear,friction reducing and antishudder properties.This ashless dispersant can effectively improve the frictional characteristics of lubricants,and effectively solve the problem of friction durability of automatic transmission fluid.