  By using Laplace transformation we developed an approximate solution to
describe neutrino oscillation probabilities in arbitrary density matter. We
show that this approximation solution is valid when matter potential V satisfy
$V< \Delta m^2/2E$ and $\int VL<1$, where $L$ is the length of the neutrino
oscillation . Thus, the formula is useful for propagation of the solar or
supernova neutrinos with terrestrial matter effect.
