Tert-dodecyl mercaptan (TDDM) was used to modify the grafting character of maleic anhydride-functionalized acrylonitrile-butadiene-styrene core-shell particles (ABS-g-MA). With the increase of TDDM content, the grafting degree and grafting efficiency of ABS-g-MA particles decrease, which induce the decrease of grafted acrylonitrile-styrene-maleic anhydride copolymer (g-SAM) and the increase of free acrylonitrile-styrene-maleic anhydride copolymer (f-SAM). The change of the g-SAM and f-SAM content modifies the chemical reactions degree at the interface and in the matrix. The interface reaction can decrease the interfacial tension and prohibit the agglomeration of ABS-g-MA particles, which have been testified by Molau test and SEM observation. The interface reaction is beneficial to the toughness improvement and the reaction in the matrix leads to higher stiffness. In the present paper, when TDDM content is 0.28 %, PA6/ABS-g-MA blend shows superior toughness and higher stiffness.