Differential　scanning　calorimetry　was　used　to　investigate　the　effect　of　polymide6　(PA6)　grafted　Kevlar　fiber　(KF)　on　the　isothermal　crystallization　kinetics　of　PA6/KF　composites.　The　results　show　that　the　isothermal　crystallization　of　PA6　is　dominated　by　nucleation　while　the　ungrafted　KF　plays　an　role　of　heteregeneous　nucleation　agent　in　the　process　of　crystallization　of　PA6　and　increases　its　crystallization　rate.　The　PA6　grafted　KF　still　plays　the　role　of　heteregeneous　nucleation　agent　in　the　PA6/KF　composites,　however,　its　effect　is　less　than　that　of　the　un-grafted　KF.　This　may　be　ascribed　to　the　improved　interfacial　adhesion　between　PA6　and　KF　in　the　composites　where　the　movement　of　PA6　segments　are　inhibited,　thus　leading　to　the　reduction　of　the　crystallization　rate　and　the　degree　of　crystallinity　of　PA6　in　the　composites.