Rotary ultrasonic applications are being widely used in machining hard and brittle materials. Conventional conducting ring used as power transmission part limits the ultrasonic applications from rotating at high speed. A high efficiency power transmission system is defined in this article to solve this problem. It consists of a contactless transformer, which was made up of two hollow copper coils, ultrasonic power supply and compensation capacitors. Four compensation methods are proposed and their properties are analyzed through simulations and experiments. The simulations show that S-S compensation is superior to others on the performance of transient and steady circuit parameters and the max transmit efficiency can reach about 97.2% when appropriate compensation method and capacitance are used. Rotary experiments show that speed has little effect on the property of the system.