Maleic anhydride grafted natural rubber compatibilizer was prepared in molten state using twin screw extruder. Amount of maleic anhydride and initiator, as well as screw rotation were varied according to Box-Behnken experimental design. Titration of acid group from the anhydride function and FTIR spectra analysis were carried out as quantitative and qualitative analysis of grafted MA, respectively. The results showed that the percentages of grafted MA for all samples were ranged from 1.31 to 5.36%. The optimum conditions are predicted at 14.4 phr of MA level, 0.41 phr of BPO level, and 71 rpm screw rotation giving 5.39 ± 0.16% of grafted MA. FTIR spectra showed that the MA and carbonyl functional group were found in the compatibilizer suggested the presence of grafted MA and ring opening reaction.