Isothermal hot compression tests of a new marine titanium alloy Ti80 were conducted on a Gleeble-3500 thermal simulator. The variation of flow stress under different processing parameters was studied and elevated temperature constitutive equation and processing map were established. Based on the analysis of high power dissipation efficiency in safe region, the initial temperature of bar stock was preliminary determined as Ti80 alloy seamless tube was prepared through rotary piercing process. Finally, the judgment was proven by 3D thermo-mechanical coupled simulation as well as physical experiment. The results show that the flow stress of Ti80 alloy varies with sensitivity of the temperature under different strain rate. The stress will increase sharply with decreasing temperature in α+β phase field; while has slight difference in single β phase field. Taking strain compensation into consideration, the modified hyperbolic-sine Arrhenius type equation could give an accurate estimation of flow stress for hot deformation of Ti80 titanium alloy. The developed processing map shows two high power dissipation efficiency domains, one is in α+β phase field with low strain rate, i.e. 925-975℃/0.01-0.1s_-1; the other is in the β regime with intermediate strain rate, i.e. 1050-1100℃/0.1-1s_-1. Finite element simulation for rotary piercing process was further conducted at initial temperature of 950, 1050 and 1100℃ for bar stocks. It is found that the plug force at temperature of 950℃ increases significantly about 4-5 times to that at temperatures in single β phase field, and what is worse, piercing in α+β phase field leads to rolled stock jamming in Diescher mill. However, the piercing process in β phase field can be conducted well. For reducing energy consumption, the temperature of 1050℃ is considered as the optimal choices. In the end, Ti80 alloy seamless tube was produced successfully in Diescher mill.