Various aspects of anaerobic digestion (AD) technology have been the focus of research in recent years. Shortening the digestion time with enhanced process efficiency is one of the integral concerns in AD technology. This study was conducted to investigate the feasibility of a two-phase anaerobic treatment system for unscreened dairy manure. Hydraulic retention time (HRT) and organic loading rate (OLR) in the hydrolytic reactor are varied in order to evaluate the effect of these factors. The results showed that an optimum HRT and OLR of 2 days and 15 g. VS/L. day, respectively, yielded maximum acidification. The separation of acidogenic and methanogenic phases of digestion resulted in a significant increase in methane production rate in the methane reactor. The methane yields were found to be 313 and 221 mL CH4/g. VS loaded in two-phase and one-phase systems at 35 degrees C, respectively.