Fifteen Dairy cattle of Holstein Crossbred heifer were used for estimating rumen microbial protein synthesis. The cattle fed by a single diet of King Grass (KG), Corn Stover (CS) or rice straw (RS) ad libitum as basal diet that was supplemented by a high protein concentrate. Microbial protein synthesis were estimated from derivatives concentration. Data obtained: microbial protein synthesis (MPS) were analyzed using analyses of variance, in split plot and completely randomized design. The means differences were analyzed by DMRT. The result of this research showed that purin derivatives concentration of cattle fed on KG, CS, and RS were 75.07; 67.72 and 61.88 mmol/day, respectively. The production of microbial protein synthesis value were respectively 55.79, 49.43 and 44.35 gN/day and it was significantly different among diet (P<0.01). The Duncan test showed that KG's diet was the highest followed by CS's diet and RS's was the lowest.