Abstract: In this study, rice, millet, purple rice and buckwheat were used as substrates for solid fermentation of Cordyceps militaris, and the total selenium contents were determined by hydride generation atomic fluorescence method. The contents of cordycepin and adenosine in matrix were determined by high performance liquid chromatography, and the contents of crude proteins and crude polysaccharides were detected by coomassie bright blue and sulfuric acid-phenol methods. On the basis of single factor experiments, response surface method was adopted to optimize the technology and formula of nutritional rice paste using organic selenium, cordycepin, adenosine, polysaccharides, proteins and sensory scores as indicators, so as to compare and analyze the ratios of brewing material to liquid and water temperatures of nutrient rice paste. The results showed that the mycelia of C. militaris could completely infect the substrates of rice,millet, purple rice and buckwheat in 15 days, and the total selenium contents were（1.8±0.3） mg/kg,（1.7±0.4） mg/kg,（1.9±0.4） mg/kg and（1.7±0.5） mg/kg, respectively. The main form of selenium is selenomethionine. Grain fermentation substrates are rich in cordycepin, adenosine, polysaccharides and proteins. The optimal drying temperature of the substrates was 50 ℃ determined by single factor experiments. The grain shape was intact and the exposed surface of mycelia were golden after drying. The preparation process and formula of selenium-rich C. militaris nutritional rice paste was optimized by single factor and response surface tests as follows: selenium-rich C. militaris grain substrates addition of50.0%, milk powder addition of 4.5%, and brewing temperature of 80 ℃. The nutritive rice paste prepared under these conditions was rich in unique fragrance of C. militaris, attractive in color and mellow in taste, which would enrich the processing types of rice paste.