Rotating BOP is a necessary equipment for under-balanceddrilling , geothermal drilling, coal-bed methane drilling. It sealed between the borehole nnulus and the drill string, Provide safe and effective  pressure control, also it can guided the circulating fluid from the wellhead. This technological development expanded the under-balanced drilling scope of use,  Such as closed-circuit, flow drilling, MWD, well test, backcycling, nitrogen injection etc . The Rotating BOP mainly comprised rotation ASSY, body and clip cylinder. The Rotation mainly comprised quadrel ASSY,central tube, bearing, sealing rubber etc.