[Objective] To explore how to deal with the paternity test of complex adoption cases. [Method] Samples from 13 families, in which adoptive parents were suspected related to biological parents, were genotyped using "Identifder + Sinofder + Powerplex 16" combined system (D8S1179, D21S11, D7S820, CSFIPO, D3S1358, TH01, D13S317, D16S539, D2S1338, D19S433, VWA, TPOX, D18S51, D5S818, FGA, D6S1043, D12S391, PentaD, PentaE) followed by further statistical analysis. [Result] Among all 13 cases, 2 were completely accordance with the Mendel law, PI > 10 000. There found more than 3 inconsistent loci in 8 cases. And found 1～2 inconsistent loci in 3 cases, needed to test more STR loci until PI≥10 000. The half sibling index (HSI) was also calculated with ITO method. The adoptive parents of 2 cases were not excluded from a full sibling with biological parents. In addition, Y-STR loci were tested for 4 cases (father/son). Two adoptive fathers of them were not excluded from the paternal relationship with biological fathers. [Conclusion] The most (76.9%) of all (13) complex adoptive cases of paternity test could be drawn a definite conclusion with combined system of "Identifder + Sinefiler + Powerplexl6". Minority (23.1%) of them was not definite yet and needed testing more STIR loci. Meanwhile, we suggested adding Y-STR tests and providing HSI for reference.