  Using first-principles method within the framework of the density functional
theory, we study the influence of native point defect on the structural and
electronic properties of Bi$_2$Se$_3$. Se vacancy in Bi$_2$Se$_3$ is a double
donor, and Bi vacancy is a triple acceptor. Se antisite (Se$_{Bi}$) is always
an active donor in the system because its donor level ($\varepsilon$(+1/0))
enters into the conduction band. Interestingly, Bi antisite(Bi$_{Se1}$) in
Bi$_2$Se$_3$ is an amphoteric dopant, acting as a donor when
$\mu$$_e$$<$0.119eV (the material is typical p-type) and as an acceptor when
$\mu$$_e$$>$0.251eV (the material is typical n-type). The formation energies
under different growth environments (such as Bi-rich or Se-rich) indicate that
under Se-rich condition, Se$_{Bi}$ is the most stable native defect independent
of electron chemical potential $\mu$$_e$. Under Bi-rich condition, Se vacancy
is the most stable native defect except for under the growth window as
$\mu$$_e$$>$0.262eV (the material is typical n-type) and
$\Delta$$\mu$$_{Se}$$<$-0.459eV(Bi-rich), under such growth windows one
negative charged Bi$_{Se1}$ is the most stable one.
