To improve the impact toughness of short glass fiber (SGF) reinforced polypropylene (PP) composite foams, maleic anhydride grafted ethylene-alpha-octene copolymer (mEOC) was employed as impact modifier and interfacial compatibilizer. And for comparison, mEOC was also introduced into PP/EOC/SGF composite barns. Then, the foaming qualities, interfacial structures and mechanical properties of samples against varying mEOC contents were examined and compared in detail. Results showed that adequate mEOC significantly improved the foamabilities of the composites, while the optimized mass fraction was 8% for PP/SGF composite foams and 3% for PP/EOC/SGE system. Increased mEOC facilitated the higher impact toughness, which was increased by 77% for PP/SGF composite fimms, whereas only 5% for PP/EOC/SGF foams. However, the flexural strengths were just improved slightly, while compressive strengths decreased monotonically with mEOC fir the investigated composite fimms.