  Measurement of the muon charge asymmetry in inclusive
$pp$$\rightarrow$$W(\mu\nu)$ + X at $\sqrt{s}$ = 8 TeV is presented. The data
sample corresponds to an integrated luminosity of 18.8 $fb^{-1}$ recorded with
the CMS detector at the LHC. With a sample of more than a hundred million
$W$$\rightarrow$$\mu$$\nu$ events, the statistical precision is greatly
improved in comparison to previous measurements. This new result can provide
additional constraints on the parton distribution functions of the proton. This
measurement is used together with the cross sections for inclusive deep
inelastic ep scattering at HERA in a next-to-leading-order QCD analysis. The
impact to the valence quark distributions is demonstrated.
