The effects of maleic anhydride-grafted polypropylene(PP-g-MAH) and maleic anhydride-grafted polyolefin elastomer(POE-g-MAH) on interfacial adhesion properties of the polypropylene/magnesium oxysulfate whiskers(PP/MOSw) composites were investigated via mechanical, thermal, ATR-FTIR and rheological tests. Although significant increases in yield strength and Young’s modulus were observed in PP-g-MAH treated composites, a sharp decline in these properties was observed in POE-g-MAH treated composites. ATR-FTIR results indicated that esterification occurred between the hydroxyl groups of MOSw and the carbonyls of anhydrides of both compatibilizers but POE-g-MAH was still incompatible with the PP matrix, as verified by the presence of shoulder peaks in DTG curves and numerous voids in SEM micrographs. On the other hand, PP-g-MAH was highly compatible with the PP matrix, as evidenced by the peaks in DTG curves and vague interfaces with wrapped melts on the surface of MOSw. Rheological behaviors also confirmed that introducing PP-g-MAH resulted in a transition from liquid-like to solid-like, which was attributed to the stronger interfacial adhesion between MOSw and the PP matrix. POE-g-MAH treated composites, in contrast to PP-g-MAH, maintained liquidlike rheological behaviors as typical molten polymers. There is likely a MOSw network formed in the PP/15PP-gMAH/15 MOSw composite as suggested by the significant deviation of G′ versus G″ plots and the two crossover frequencies observed in plots of tan? versus frequency. The effects of maleic anhydride-grafted polypropylene (PP-g-MAH) and maleic anhydride-grafted polyolefin elastomer (POE-g-MAH) on interfacial adhesion properties of the polypropylene / magnesium oxysulfate whiskers (PP / , thermal, ATR-FTIR and rheological tests. Although significant increases in yield strength and Young’s modulus were observed in PP-g-MAH treated composites, a sharp decline in these properties was observed in POE-g-MAH treated composites. ATR-FTIR results indicated that esterification occurred between the hydroxyl groups of MOSw and the carbonyls of anhydrides of both compatibilizers but POE-g-MAH was still incompatible with the PP matrix, as verified by the presence of shoulder peaks in DT micrograms and numerous voids in SEM micrographs On the other hand, PP-g-MAH was highly compatible with the PP matrix, as evidenced by the peaks in DTG curves and vague interfaces with wrapped melts on the surface of MOSw. Rheological behavio rs also confirmed that introducing PPG-MAH resulted in a transition from liquid-like to solid-like, which was attributed to the stronger interfacial adhesion between MOSw and PP matrix. POE-g-MAH treated composites, in contrast to PP -g-MAH, maintained liquidlike rheological behaviors as typical molten polymers. There is likely a MOSw network formed in the PP / 15PP-gMAH / 15 MOSw composite as suggested by the significant deviation of G ’versus G "plots and the two crossover frequencies observed in plots of tan? versus frequency.