[en] A new parametrization of polarized parton distribution functions is discussed in the leading (LO) and the next-to-leading order (NLO) of QCD. Taking account of the positivity and the counting rule of parton distributions and assuming the SU(3) flavor symmetry for the sea-quark, polarized parton distribution functions for valence u, d, sea-quark and gluons are determined form the fit to world data of spin asymmetries in polarized deep inelastic scatterings. The amount of the sum of quark spin, ΔΣ, carrying the nucleon spin in the NLO is rather small compared with the one of other works done so far. (author)