In order to solve the vibration problems of offshore wind turbines (OWTs) under the excitation of wind, wave and earthquake, a semi-active control method based on magnetorheological elastomer (MRE) tuned mass damper (TMD) was proposed. Firstly, the variable stiffness filed-induced characteristics of MRE and the design principle of MRE-TMD were introduced. Then, a dynamic model of OWT-TMD was established, and the excitation loads of wind, wave and earthquake were calculated. Next, the semi-active control algorithm was applied to track and identify the frequency of responses at the tower top of OWT, and the stiffness of MRE-TMD was adjusted in real time and then the vibration of OWT was controlled. By analyzing the dynamic response of the jacket supported OWT under the multiple loads, the results show that the MRE-TMD can effectively attenuate the vibration of the OWT. Compared with passive TMD, MRE-TMD presents better vibration reduction effects, which provides a new solution control of OWT.