Abstract: A quantitative detection method based on droplet digital PCR(ddPCR)technique was established to determine the purity of donkey-hide gelatin and its subsidiary products. The results showed that in a given range,the correlationship between raw gelatin weight and DNA concentration and between DNA concentration and target DNA copy number were both close to linear. Using DNA concentration as intermediate,the linear formula between raw gelatin weight M(mg)and target DNA copy number C(copies/μL),M=0.13C+3.05,was calculated out. Thus,gelatin quantification was carried out in the samples by the formula between raw gelatin weight and target DNA copy number,which was calculated by ddPCR. Accuracy test showed that measured value was basically the same as the real value and the maximum deviation was just 4%,which indicates that the method was accurate and reliable. Using this method,8 gelatins and 2 gelatin instant powder in the market were tested. Results showed that,in 8 gelatins,3 were relatively pure and 2 of them had low gelatin content and the lowest was just 23.3%. The content of gelatin in 2 gelatin instant powder was 44.8% and 39.8%,respectively. This showed that this method could be used effectively in quantitative detection and purity identification for donkey-hide gelatin and its subsidiary products. The quantitative detection method based on ddPCR in this paper was accurate,efficient and stable. It had great application value and application prospect,which can effectively prevent the occurrence of gelatin adulteration.