Objective Kunming strain(KM) mice were used as animal models. Nontoxic dextran conjugated with tetramethylrhodamine（TMR）and fluorecein isothiocyante（FITC）was microinjected to two of the 2-cell blastomere as molecular probe to trace the development fate of the blastomere ,in order to figure out the mechanisms of the formation of Em-Ab axis. Methods FITC- dextran was injected to zygote in order to make sure if it is noxious. Two blastomeres of 2-cell embryo were injected FITC- dextran and TMR- dextran respectively. Results When labeled embryo develeped to blastocyst, distribution of progeny of 2-cell embryo blastomeres can be detected.Conclusion The cells of blastomere randomly distributed either embryonic parts or extra