  In this talk, we report our recent work on the pion weak decay constant
(F_pi) and pion mass (m_pi) using the nonlocal chiral quark model with the
finite quark-number chemical potential (mu) taken into account. Considering the
breakdown of Lorentz invariance at finite density, the time and space
components are computed separately, and the corresponding results turn out to
be: F^t_pi = 82.96 MeV and F^s_pi = 80.29 MeV at mu_c ~ 320 MeV, respectively.
Using the in-medium Gell-Mann Oakes-Renner (GOR) relation, we show that the
pion mass increases by about 15% at mu_c.
