Four-ball machine was selected to study the friction performance of ZDDP in 250N base oil.The test was carried out under different ZDDP addition amount,load,speed and test time.The influence of each test condition on the friction performance of ZDDP was observed.The influence of four factors on ZDDP was analyzed by orthogonal test method.The test results show that at 950 r/min,ZDDP has better antiwear performance under 296 N load compared with 196 N and 392 N load.At 1 200 r/min,the wear scar diameter is decreased slowly with the increase of ZDDP content.At 1 450 r/min,the base oil with ZDDP cannot provide effective lubrication under 392 N load,resulting in severe wear.The results of orthogonal test indicate that under the selected test factors and levels,the significance of the influence on the wear scar diameter is in the order of load,speed,addition amount of additive and time,and the addition amount of additive and time have close influence on the absolute value of wear scar diameter change