Agricultural biomasses that are not edible contain many raw resources that can produce valuable products. Rice husk and straw are a byproduct which is generated during rice production this biomass consists high percentage of silica and candidate as an alternative source of silica. Conventional silica production uses high energy. This study aimed to use rice husk and straw for the production of silica. Silica was prepared by sol-gel method from rice husk and straw, initially, the mixture of rice husk and straw were cleaned, acid-treated and incinerated at a temperature of 700 oC to form ash then the ash was reacted with a different molar concentration of NaOH at different temperature for different time to analyze their effect. After the reaction, sodium silicate solution was formed finally titrated with 1 M solution of HCl, and silica gel was produced. CCD under design expert software was used to determine the effect of experimental variables and the significance of the parameters were analyzed by ANOVA. The optimum parameters can generate a yield of 97.01wt % which shows high purity of silica can be obtained from mixed rice husk and rice straw. The functional groups those exist on the surface of silica were characterized by FTIR and surface area was determined by sears method and value of 759 m2 g-1 was measured for surface area. The moisture-absorbing efficiency was also tested and compared to commercial silica and a value of 23.7 % was obtained for this study. Generally it was possible to produce silica with 97.01 wt % from mixed rice husk and straw at 2.07 M NaOH concentration, at digestion temperature of 95oC and digestion time of 2.7 hr.