  The power-Lanczos (PL) method is one kind of Green's function Monte-Carlo
simulation, which is improved by Lanczos iterations. The ground state energies
of strongly-correlated models can be evaluated by this method quite accurately.
In this report, the boundary of phase separation (PS) of the two-dimensional
$t-J$ model is investigated by the power-Lanczos method and Maxwell
construction. The energies are compared with the results evaluated by other
methods. Our conclusion is that there is no phase separation for $J/t \le 0.4$.
