The pressure induced superconductivity and structural evolution for Bi2Se3 single crystal have been studied. The emergence of superconductivity with onset transition temperature (Tc) about 4.4K is observed around 12GPa. Tc increases rapidly to the highest 8.5K at 16GPa, decreases to 6.5K at 21GPa, then keep almost constant. It is found that Tc versus pressure is closely related to the carrier density which increases by more than two orders of magnitude from 2GPa to 23GPa. High pressure synchrotron radiation measurements reveal structure transitions occur around 12GPa, 20GPa, and above 29GPa, respectively. A phase diagram of superconductivity versus pressure is obtained.
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