Abstract： Objective To analyze the clinical outcomes of patients treated with in vitro fertilization and embryo transfer (IVF-ET) and influence factors of pregnancy rate. Methods We retrospectively analyzed the clinical data of 12 491 cycles, including 6832 fresh IVF/intracytoplast single sperm injection (ICSI) cycles and 5659 frozen embryo transfer (FET) cycles from 2005 to 2007. Results The clinical pregnancy rate per cycle was 32. 99% (2254/6832)in fresh embryo transfer program, and the live birth rate was 25.75% (1394/5413); the early pregnant loss rate was 9. 36% (211/2254), and the prenatal defect rate was 1.45% (25/1722). Through analysis of these patients' basic data, we found that the patients' age, causes for infertility, egg retrieval and cycle number affected the pregnancy rate. Using logistic regression method, we found that patients′ age was the most important factor affecting pregnancy outcome. In FET cycles, the clinical pregnancy rate was 38.08% (2155/5659), significantly higher than fresh embryo transfer cycles. Conclusions IVF-ET treatment is a safe and effective method for infertility couples. However, the female age and poor ovarian response are the main factors affecting pregnancy rate. Thawed embryo transfer can increase the accumulated pregnancy rate effectively.