Abstract: An experiment was conducted to improve the quality of palm kernel cake (PKC) through fermentation by combination of substrate composition and inoculum dosage. The experiment used complete randomize design (CRD) with 4 x 3 factorial and twice replication. The first factor was substrate composition(A): (1) PKC 80% + 20% of rice brand, (2) PKC 80% + 20% of feses, (3) PKC 70% + 30% rice brand, (4) PKC 70% + 30% of feses. The second factor was inoculum dosage (B): (1) 5%, (2) 10% and (3) 15%. The parameters were protease and cellulase activity, crude protein and crude fiber of palm kernel cake fermentation. The result of study showed that there was significantly (p<0.05) interaction between substrate composition and inoculum dosage to protease and cellulase activity, crude protein and crude fiber of palm kernel cake fermentation. Every factor from substrate composition and inoculum dosage showed that there were highly significant (p< 0.01) effect to protease and cellulase activity, crude protein and crude fiber of palm kernel cake fermentation. It can be concluded that palm kernel cake which was fermented by combination of substrate composition and inoculum dosage showed that substrate composition 80% PKC + 20% rice brand and inoculum dosage 10% had a better nutrient content of Palm kernel cake fermentation. This condition can be seen in protease activity (18.10 U/ml) cellulase activity (22.84 U/ml) crude protein (20.84%) and crude fiber (10.64%).