Abstract: While underbalance drilling spreads greatly, rotating blowout preventer, as a kind of high technical product, is the crucial equipment to control well pressure.A new rotating blow out preventer has being manufactured and tested.It is desig ned referring to current main similar product in its main preferences.There are many difficulties during the new rotating blow out preventer's manufacture and test, they concentrate on spherical seal, dynamic seal and bearings.These different parts' work lives determine whether the rotating blow out preventer can run to complete its task.After compared and tested several kinds of parts worldwide many times during simulating underbalance drilling in plant, advanced parts are used in the new rotating blow out preventer to solve the problems above.So get advanced part s, make high technical products.The primary success of the new rotating blowout preventer is resulted from many tests that cost much of time.