Objective To investigate whether the embryo cleavage rate on day 3 of fertilization can predict the blastocyst development potential and clinical outcome of assisted reproduction. Methods The embryo implantation data of 366 fresh blastocysts and the clinical data of 150 infertility patients undergoing in vitro fertilization or intracytoplasmic single sperm injection-embryo transfer (IVF/ICSI-ET) in our center from Jan. 1, 2016 to Dec. 31, 2018 were retrospectively analyzed. According to the cell number of the blastomere on the third day of fertilization, embryos were divided into slow development group (≤ 6 cells, n=78), normal development group (7-9 cells, n=230) and fast development group (≥ 10 cells, n=58). The blastocyst formation rate, high quality blastocyst formation rate, embryo implantation rate, clinical pregnancy rate and live birth rate of the 3 groups were compared. Results The blastocyst formation rates of the slow, normal and fast development groups were 7.7% (6/78), 55.7% (128/230) and 29.3% (17/58), respectively, and the normal development group had the top rate, with significant difference when comparing with those in the other two groups (both P<0.01); the high quality blastocyst formation rates of the 3 groups were 0 (0/6), 7.0% (9/128) and 11.8% (2/17), respectively, and the highest rate was found in the fast development group, with significant difference when comparing with that in the normal development group (P<0.05); the embryo implantation rates of the 3 groups were 0 (0/18), 50.6% (80/158) and 63.3% (19/30), respectively, and the highest rate was found in the fast development group, with significant difference when comparing with that in the normal development group (P<0.05); the clinical pregnancy rate and live birth rate were 53.7% (58/108) and 41.4% (24/58) in the normal development group, and were 63.0% (17/27) and 47.1% (8/17) in the fast development group, respectively; there were significant differences in clinical pregnancy rate and live birth rate between the normal and fast development groups (both P<0.05). Conclusion The cleavage embryos with 7-9 cells on day 3 of fertilization have the highest blastocyst formation rate, and cleavage embryos with ≥ 10 cells on day 3 have much higher rates of high quality blastocyst formation, embryo implantation, clinical pregnancy and live birth, suggesting that fast development embryos have normal development potential.