Three new N-alkylsulfonamide-containing phenylazopyrazolone dyes have been synthesized by reaction of sulfonyl chloride intermediates with different saturated aliphatic amines and their molecular structures were confirmed by FTIR, 1H NMR and MS.The dyes were applied to unmodified polypropylene fabric. These dyes showed high exhaustion as well as higher levels of fastness to washing, sublimation and rubbing compared with C.I. Disperse Yellow 16. The results showed the N-alkylsulfonamidecontaining dyes were suitable for dyeing unmodified PP fiber and exhibited good color depth and fastness properties.