In this study， we developed an accurate and reliable ddPCR-based method for identifying and quantifying duck derivative in beef. Single-copy nuclear gene ACTB encoding a β-Actin was selected and used as the target to designed specific primers and probes for both beef and duck. In order to transform the ratio of DNA copy number to the mass fraction of targeted meat， a fixed constant (transfer coefficient) was introduced， which was designated as K. Based on the relationship between the known mass fractions in simulated meat mixtures and the actual DNA copy numbers measured by ddPCR， the K value was calculated and validated. A quantitative formula was consequently established and applied for quantifying the content of duck in both the artificial duck/beef-mixed samples and commercial beef products. The results revealed that the established ddPCR method was highly specific for the detection of duck-derivative in beef. The K value was 0.16 and hence the quantitative formula was established as MD/MB=0.16×QD/QB， where MD and MB refer to the mass of duck and beef， respectively. QD and QB refer to the copy number of the target gene detected in the ddPCR assays， respectively. The linear regression was established within the duck content of 1%-90% with the correlation coefficient (R2)≥0.99. The limit of detection (LOD) and limit of quantification (LOQ) of the established ddPCR method are 0.1% and 0.5%， respectively. When the artificial mixed samples with the duck content of 20%-80% were detected， the absolute errors were all <1%. Duck derivative was detected in two out of 16 commercial beef products， with the content of 44.87% and 18.21%， respectively， which were inconsistent with statement on the product labels. In summary， the ddPCR method developed in this study demonstrated good specificity， sensitivity， accuracy and applicability for quantifying duck derivative in beef， could provide technical support for the quality and safety inspection of beef and beef products in China.