  We calculate the two leading-twist transverse momentum dependent distribution
functions of the pion meson, the unpolarized distribution
$f_{1\pi}(x,\bm{k}^2_T)$ and the Boer-Mulders function $h_{1\pi}^\perp
(x,\bm{k}^2_T)$, using the pion wave functions derived from a light-cone
approach. The evolution effect of the first $\bm k_T$-moment of the pion
Boer-Mulders function is studied by employing an approximate evolution kernel.
Using the model resulting distributions, we predict the transverse momentum
weighted $\cos2\phi$ azimuthal asymmetry in the unpolarized $\pi^- p$ Drell-Yan
process which can be measured at COMPASS in the near future.
