Pronucleus transplanted mice have been produced, but their donor male pronuclei were derived from mature sperm and were completely synchronous with female pronuclei because both male and female pronuclei came from the same fertilized oocyte. The present study firstly produced male pronuclei by introducing round spermatids into enucleated mouse oocytes, then transferred the male pronuclei into mouse oocytes at three activation stages and finally compared the effect of three kinds of oocytes on the development of reconstructed embryos. Our results indicate that, in enucleated oocytes, mouse round spermatid nuclei can transform to male pronuclei in a higher proportion, and the synchronization between male and female pronucleus does not significantly influence the early cleavage but the later and full-term development of reconstructed embryos.