For a Poisson algebra, we prove that the Poisson cohomology theory introduced in [M. Flato, M. Gerstenhaber and A. A. Voronov, Cohomology and Deformation of Leibniz Pairs, Lett. Math. Phys. 34 (1995) 77-90] is given by a certain derived functor. We show that the (generalized) deformation quantization is equivalent to the formal deformation for Poisson algebras under certain mild conditions. Finally we construct a long exact sequence, and use it to calculate the Poisson cohomology groups via the Yoneda-extension groups of certain quasi-Poisson modules and the Lie algebra cohomology groups.Proposition 1.2 (Proposition 4.5). Let P = (A, ·, {−, −}) be a nontrivial commutative Poisson algebra. If HP 2 (A) = 0, then P has no deformation quantization.A well-known result by Farkas and Letzter says that a prime noncommutative algebra admits only standard Poisson structures([4, Theorem 1.2]). In some sense,