TB6 titanium alloy square bar was isothermal forged by isothermal forging press in this research,the forged billets were cooled by different ways that water quenching and air cooling. The forged billets by water-quenched were aged and the forged billets by air-cooled were solid solution and aged after cooled. The effects of different heat treatments on the microstructure and mechanical properties of TB6 titanium alloy after isothermal forged were studied.The results show that alpha phase size of TB6 titanium alloy by water-quenched after isothermal forged is smaller than that by air-cooled after isothermal forged,there is no induced alpha phase in beta base of titanium alloy by waterquenched and there is induced alpha phase in beta base of titanium alloy by air-cooled. The precipitated secondary alpha phase of titanium alloy by water-quenched after aged is more chaotic than that by air-cooled after solid solution and aged. After isothermal forged,the strength and plasticity of TB6 titanium alloy by water-quenched after aged are similar to that by air cooled after solid solution and aged,but the fracture toughness of the former is higher than that of the latter.