Abstract: In this study, the effect of oxide added to soda oxygen anthraquinone (SOAQ) pulping process in precipitated onto the pulp of silica in rice straw during pulping was investigated. Oxide added SOAQ pulping methods was used to increase silica precipitation on pulp by adding 0.5-1.5% metal oxide such as Al2O3, CaO and MgO. As a results of the data obtained, optimum oxide added soda-oxygen-anthraquinone pulping condition of rice straw were as follows: Alkali charge on oven dry (o.d) raw material: 15%, anthraquinone (AQ) charge (on o.d raw material): 0.1%, Al2O3 charge (on o.d raw material): 1.5%, temperature: 130oC, time at max. temperature: 45 min., oxygen pressure: 6 kg cm-2 and liquor to straw ratio: 5/1. Precipitated silica rates onto pulps were 80.54 and 94.65% for SOAQ and oxide added SOAQ pulping methods, respectively.