Using Opto-electronic detection technology, marking miRNA and isothermal rolling circle amplification and detecting markers which excite fluorescence intensity, we have designed a new portable device for the rapid detection of miRNA, the recognition system of characteristic fluorescence analysis was established eventually. we have got the point that there is the linear relationship (R2=0.999 1) between miRNA concentration and fluorescence intensity at the time that the miRNA concentration range the instrument can measure is in the range of 0.01~0.1 μmol by changing the excitation light intensity, miRNA reagent concentration and other parameters, meanwhile, we also know that it is 7 copies that the lowest values the instrument can measure in theory.