Conventional annealing is a simple and feasible processing for most α+β titanium alloys. The thermal stability and other high temperature properties of TC6 titanium alloy at conventionally annealed state have been studied and compared with those at duplex-annealed and isothermally annealed states. The results show that, both of TC6 taitanium alloy bars and forgings at conventionally annealing state have excellent microstructure and mechanical property stability after exposure at 300℃ over 5000h. The tensile, creep and rupture properties at different temperatures after conventional annealing are equivalent to those after duplex-annealing and isothermal annealing. The properties of bars and forging products of TC6 titanium alloy can meet the demands of aircraft structure parts under 300℃ application condition.