The objective of this study is to improve and simplify the method for splitting embryo. This study provides the simplest splitting method without micromanipulator. With the aid of a common stereomicroscope, embryos are bisected using a glass needle by hand. Only about one minute is required for each embryo to bisected in this way. A total of 701 four-day mouse embryos were bisected and 1346 demi-embryos (96.01%) were successfully produced.The developmental rate of demi-embryos in vitro culture is 73.70% ( divided blastocysts 72.88% and divided morulae 74.22% ) .There was no significant difference in the developmental rate of demi-embryos in vitro culture between blastocyst and morulae. The developmental rate of demi-embryos without zona pellucida in vitro culture of with 20% fetal calf serum or 20% sheep serum or 20% equine serum was 64.95%, 73.54% and 76.03% respectively. Moreover there was also no significant difference between them. The developmental rate of the frozen/ thawed demi-embryos with or without zona pellucida and demi-embryos with zona pellucida embedded in agar in vitro culture was 26.67%, 56.67% and 64.29% respectively.