Abstract: Objective To develop a method for the detection of micro RNA346 gene polymorphism by capillary electrophoresis (CE). MethodsThe genome DNA was extracted with the kit of blood/cell/tissue genome DNA extraction, then micro RNA346 gene was amplified by PCR, digested by BciT130Ⅰrestriction enzyme and detected by CE. The conditions for CE separation were optimized. Samples from rheumatoid arthritis patients and healthy persons were detected under the optimal conditions. ResultsUnder the optimized experimental conditions of CE (sieving medium mass concentration was 10 g/L and the separation voltage was 12 kV), the detection of the digested products of microRNA346 gene could be completed within 25 min. The intra-day relative standard deviation (RSD) of the method was 0.43%-0.63% and inter-day RSD was 1.49%-1.56%.Samples from 96 rheumatoid arthritis patients and 43 healthy persons were analyzed by the proposed method. The results showed that only micro RNA346Ⅰtype was detected but micro RNA346 Ⅱ type wasn’t. ConclusionThis method is easy to operate, and has the advantages of high efficiency, fast speed, less sample consumption and high automation level. This method is suitable for the determination of RNA gene polymorphism of mirco RNA.