Wave Energy have being developed for more than 200 years. The first patent for wave energy converter could date back to 1799 by the Girard. For the past decades, wave energy’s development has being a rather hot field. Much more than1000 patents were filed. Among all the devices that were filed, heaving buoy is an important form. It is named the 3rd generation wave energy convertor. The device contacts the wave directly so its conversion efficiency is really high. Also it is much smaller than other forms. What’s more, it is adaptable to several of water depths with the help of mooring system. A device named Archimedes wave swing by Teamwork Technology BV claimed to had reach the capacity of 2 MW. That’s why this type was chosen to be the wave energy convertor of “300kW Ocean Energy Integrated Power Supply System” project in China. According to Hulme’s research, the best radius for single buoy can be calculated by. It is tested that the buoy of best radius only response to a narrow width of frequency efficiently. However, the wave in the real sea was combined of different kind of frequency, especially in China Sea. Moreover the size of the buoy with best radius is very bigger, which makes it not that economic. For these reason, the heaving buoys was invented. One of those devices consists of several single buoys with smaller radius. This article focuses on the study of this form. This device, named the heaving buoys, and it is made up of 2 parts: the upper structure and the mooring system.