Abstract: Emergency Overspeed Governor is the most important protection device for reliable operating of high speed turbo-machine and also the major safety item of the modern large steam turbines. There are two types of construction, such as ring type and bolt-type. Their philosophy is the same.Since the governor appeared its static calculation has been published at home and abroad, dut dynamics problems are left out of account. According to the dynamics feature of their compound motion, the law of radial motion of bolt (or ring) with spring rotating at high speed in the holes is showed in this paper, such as dynamics characteristic, relation of construction factors and deriven calculation formulae available to design and adjust.The accuracy of theory analysis was checked by experiments in practice.