The effect of solution treatment temperature (STT) (ranging from 935°C to 995°C) on the microstructure evolution of α"-phase, α'-phase and microhardness of TC11 titanium alloy were investigated systematically by means of optical microscope, electron microscope with energy dispersive spectroscope, X-ray diffractometer and microhardness tester. Results show that the crystal structure of α"-phase gradually correspond to the crystal structure of the α' phase, and the phase composition of TC11 alloy changes with increasing STT (α+α", α+α"+α', α+α', α'). Microhardness of the alloy solution treated in the temperature range from 935~985°C increased with the solution temperature, whereas the microhardness reduced for further increase of solution temperature up to the range of 985~995°C. Microstructural features resulting from different STTs were correlated with corresponding microhardness values. With the increment of STT the microhardness increased, because the thickness and spacing of α'-lamellae increased slowly and the β-transformed structure grew up slowly. Besides, due to phase transition strengthening (PTS) the α"-phase and α'-phase are precipitated in the β-transformed structure, and the α'-lamellae contents in the β-transformed microstructure increased, eventually reaching a maximum at 985°C. Above 985°C the microhardness decreased, because the thickness and spacing of α'-lamellae increased significantly and the β-transformed structure became coarser at the expense of α'-phase and α"-phase contents.