Sine movable tooth drive has the smallest radial size. Working efficiency is one of the important factors of the performance evaluation of the drive. Here, based on analyzing entrainment speed and forces of sine movable tooth drive, the equations of the minimum oil film thickness and meshing efficiency for the drive is proposed. The minimum oil film thickness and meshing efficiency of the drive is studied, and the changes of the meshing efficiency along with main parameters are analyzed. Results show that the minimum oil film thickness between the movable teeth and central input shaft is higher than that between the movable teeth and shell, and the meshing efficiency of the drive is between 79.74% and 84.67%, and the average efficiency is 82.48% which is near the experimental result of 82.25%.