Based on Hamrock-Dowson and film thickness calculation formulae, the EHD film thickness formulae of globoidal indexing cam mechanism of steel ball between steel ball and cam raceway were deduced. By using numerical analysis method, film thickness of cams with modified constant velocity motion curve, modified trapezoidal acceleration motion curve and modified sine acceleration motion curve respectively were compared during the entire indexing cycle. The effects of cam speed, load torque on indexing plate, ball diameter, indexing plate diameter, curvature ratio, etc. on film thickness were also discussed. It provided theoretical basis for the lubrication design of globoidal indexing cam of steel ball.