Developing processes of alternative energy for fossil fuel is increasing interest because of both environmental and economical aspects. Increasing price of fossil-based products together with increasing of environmental pollution are potentials for increasing interest for sustainable and renewable energy sources. Among the renewable energy technologies such as waterfall, solar, wind, and so on, biogas production from organic matter present in industrial wastes has had growing attention during last decades. Biogas is mainly composed of methane and carbon dioxide produced as a result of synergistic interaction of bacterial community so called anaerobic digestion. Anaerobic digestion involves the degradation and stabilization of degradable organic materials under anaerobic conditions by different bacterial groups including acidogenesis, acetogenesis, and methanogenesis bacteria, which lead to the formation of biogas and microbial biomass. High straight wastewaters from food, dairy, and beverage industries as well as agricultural wastes are good options for this purpose. Anaerobic digesters often exhibit significant stability problems that may be avoided only through appropriate control strategies. Such strategies require, in general, the development of appropriate mathematical models, which adequately portray the key processes that take place. In this research, modeling and simulation of a two stage system for anaerobic digestion of potato leachate was performed. In order to perform the anaerobic digestion under optimum conditions, hydrolysis and acidogenesis steps were performed in a mixed reactor followed by methanogenesis in a UASB reactor. Known amount of sliced potato was placed in a first reactor and after hydrolysis and acidogenesis activities, flow rate containing acetate was transferred to second reactor which methane and carbon dioxide were produced under methanogenesis activity. Both reactors were operated under mesophilic temperature at 37 °C. There were assumed that both mixed and UASB reactors were completely mixed and no methane was produced in the first reactor. The influence of hydraulic retention time and inlet concentration of wastewater on the response parameters of COD removal efficiency, methane production efficiency, concentration of volatile fatty acids leaving the first reactor, and concentration of acetate leaving the second reactor were predicted and compared with experimental data. By increasing the hydraulic retention time up to 4 days, removal efficiency of COD was increasing up to 80.65%, while removal efficiency of COD was constant at hydraulic retention times more than 14 days. Yield of methane production was decreased by increasing hydraulic retention time. These results have been observed in experimental data when system has been stabilized with respect to hydraulic retention time after 17 days. At hydraulic retention times less than 17 days, the concentration of volatile fatty acids especially acetate was increasing in the first reactor which cause inhibitory effects on the methanogenic activity of the second reactor. This shows the importance of control of the two-stage anaerobic digestion which utilization and conversion of acetate in the first reactor is not performed. Therefore, concentration of acetate and its inhibitory effect should be monitored. After this overload, system was checked and stabilized. After this time, system was working steadily and results of model were comparable to experimental data. Keywords: Biogas, anaerobic digestion, UASB reactor, potato leachate, two-stage, mesophilic