Objective：To investigate the effect of female body mass index（BMI）on the outcomes of IVF/ICSI cycles after fresh embryo transfer. Methods：The data of 1 784 cycles，which were accomplished with single fresh embryo transfer in the first IVF/ICSI treatment，are analyzed retrospectively，the cycles were divided into four groups according to the recommended Chinese BMI cut-off：underweight（150 cycles，BMI<18.5 kg/m2），normal weight（1 098 cycles，18.5 kg/m2 ≤ BMI < 24.0 kg/m2），overweight（437 cycles，24.0 kg/m2 ≤ BMI < 28.0 kg/m2），obese（99 cycles，BMI ≥ 28.0 kg/m2），and the cycles were also subdivided into IVF and ICSI group by different insemination methods. We compared the number of oocytes，clinical pregnancy rates，implantation rates，live birth rates，miscarriage rates among the four groups，and also compared the fertilization rates and the high quality embryo rates among the subgroups. Results：The number of oocytes retrieved in the underweight group was significantly higher than those of the other three groups，and the number of oocytes retrieved in the obese group was significantly lower than those of the other three groups（P < 0.01）. The clinical pregnancy rate of overweight group was significantly lower than that of normal weight group，and the implantation rate of overweight group and obese group was significantly lower than that of normal weight group；the live birth and miscarriage rates in the four groups were no significant difference（P > 0.05）. There were no significant difference in fertilization rates and high quality embryo rates between the IVF subgroup and the ICSI subgroup（P > 0.05）. Conclusion：Female obesity has a significant negative effect on the outcomes of IVF/ICSI cycles. Compared with women with normal BMI，overweight and obese women decrease implantation rates after the fresh embryo transfer.