The method of measuring rice protein with fully automatic Kieldahl azotometer by single-factor experiment and orthogonal experiment was investigated. It defines the best experiment conditions through examining such key factors as sample weight, additive amount of sulfuric acid, digesting temperature and digesting time. The results showed that when the sample weight is 0.40 g, the added amount of sulfuric acid was 12 mL, digested at is 420 ℃ and for 50 min, the experimental effect was the best. The standard deviations of 6 determinations of 5 kinds of rice were 0.050 2～0.101 1, and the recoveries of nitrogen of urea were 99.9%～100.5%. The ratios of protein obtained by semi-micro distillation method were between 1.023 4～1.079 4, and the time of determination could be shortened to 1 hours. The method was found stable and accurate.