Aerial work carriage is a very important apply domain for slewing drive, usually it is very necessary of higher safety coefficient for main engines of all the aerial work carriages. The security of slewing drive is a key factor for most customers to choose it as the component of aerial work carriage; on the other hand, the worm gear and endless screw has larger speed ratio, which improve the security factor the main engine, at same time it can save a reducing device with worm gear and endless screw. As a result, the producing cost of main engine is reduced.