Rice straw as a Lignocellulose substance, profuse of Carbohydrate, is a suitable substance for the production of biogas which is a reversible biological energy. Considering the problem of supplying water in the world and Iran, application of processes with low consumption of water is necessary. This study is conducted during three phases. The first phase is dealt with investigating the effect of F/I in the production of biogas on two untreated substrates of rice straw, and pretreated with NaOH solution 8% (w/w) in the temperature of 100°C for 60 minutes, in the range of wet to dry process from the total solid amount of 0.5% to 20%. This phase was conducted in various ratio of F/I and specified that untreated rice straw in F/I=3 with the production of 153.6 mL/g VS, and pretreated rice straw in F/I=1 with the production of 146.7 mL/g VS Methane are the optimized amounts. In the second phase in the optimized ratio of F/I=3, the effect of C:N in various humidity was investigated and the ratio of C:N for Substrate was adjusted on 25 with the usage of Urea 46.7%. Unlike the anticipation, the amounts of Methane production were very low. So with conducting experiment it was specified that Inoculum contains so much Nitrogen and it isn’t necessary to add Urea. The third phase was conducted in optimized ratio of F/I=3 on untreated rice straw and three various pretreated rice straw. Sampling was conducted in different humidity degrees without adding Urea. Pretreating with NaOH solution 8% (w/w) in 100°C for 0, 30, and 60 minutes was conducted. Sampling in total solid amounts of 10%, 15%, and 20% and Hansen Method was done. In this phase, the experiment of the production of biogas on the resulted liquid of all three pretreated was done that all of them produced no gas. In all four samples, the sample with the total solid 10% produced the highest amount of methane. And meanwhile, the pretreated sample in zero minute with the production of 117.6 mL/g VS has produced the highest amount of Methane. Among Hansen Method samples, the pretreated sample in zero minute with the production of 269 mL/g VS has produced the highest amount Methane. Key Words: Biogas production, solid wet state, rice etraw, alkali pretreatment, anaerobic digestio