Abstract: ObjectiveThe present experiment was conducted to investigate effect of recipient embryo age on homing of chicken primordial germ cell ( PGC ) after transplantation and determine optimal reinjection time window , in order to provide basis for productivity of transgenic chicken. MethodPGCs were isolated from embryos of native yellow feather chicken in Guangxi, and cultured in vitro, then genetically modified, finally transferred back into recipient embryos. On the 5th days after transplantation, the gonads of recipient embryos were isolated and imaged to compare effect of recipient embryo age(14HH-17HH) on PGC migration to gonads. ResultThe mortality rate of embryo ranged from 30.0% to 60.9% after transplanting PGC at embryonic age of 14HH-17HH, with non-significant differences(P>0.05). According to number of migrated GFP-positive cells , the gonads were classified into six grades ( I-VI ) . With the increase of embryo age , PGC migration efficiency decreased gradually. When transplanting PGC at age of 14HH , the GFP-positive cells in gonads were mostly grouped in Grade V ( 40 . 0%); when transplanting PGC at the age of 15HH , the GFP-positive cells in gonads were mostly grouped in Grade III (42.1%); when transplanting PGC at the ages of 16HH and 17HH, the GFP-positive cells in gonads were mostly grouped in Grade II(45.4% and 54.5%). The highest grade of gonads(VI) appeared only in the transplantation of PGCs at the age of 14HH. ConclusionWith the increase of embryo age, PGC migration efficiency decreased gradually. In view of difficulty level in actual operation, the optimum time window for chicken embryo used in PGC transplantation is at the age of 14HH(incubation for 50 h).