Abstract: According to the meshing characteristics of double involute gears profile and the elastohydrodynamic lubrication theory, a calculation model of film stiffness of double involute gears was established to study on the change rule of film stiffness. The difference of film stiffness between double involute gears and involute gears was analyzed by contrast method, and the influence of tooth profile parameters and working conditions was studied. The analysis showed that double involute gears had a big difference in the film stiffness compared with involute gears, due to the effect of tooth waist order. Film stiffness decreased with the increase of the height coefficient of tooth waist. Film stiffness basically remained unchanged when the tooth waist tangential modification coefficient changed. The film stiffness decreased with the increase of rotational speed and increased with the increase of load increment factor.