Objective: To analyze the pregnancy outcome and influencing factors related to live birth rate of single cleavage-stage embryos, double cleavage-stage embryos and single blastocyst transfer in elderly patients (40≤age≤50 years) who underwent frozen-thawed embryo transfer. Methods: The elderly patients undergone frozen-thawed embryo transfer from January 2010 to June 2018 were enrolled. The patients were divided into three groups according to the number and stage of transferred embryo: Group D3(Day3, embryo transferred was the third day after fertilization, n=1 363), Group 2D3(two embryos transferred were the third day after fertilization, n=5 248) and Group BT (blastocyst transferred was the fifth or sixth day after fertilization, n=495). Live birth outcome was analyzed and related influencing factors were explored by multivariate Logistic regression. Results: There were significant differences in live birth rates (6.53% vs. 13.38% vs. 18.38%) between the three groups（D3, 2D3, BT）(P<0.01). Twin live birth rate was the highest in 2D3 group (1.12% vs. 7.98% vs. 1.10%)(P<0.05). Multivariate logistic regression analysis revealed that when 2D3 was taken as the reference group, the live birth rate of D3 group was lower (OR=0.558, 95%CI 0.440-0.707, P<0.001), and the live birth rate of BT group had a trend of rising (OR=1.257, 95%CI 0.977-1.617, P=0.075). The live birth rate was negatively correlated with the increase of age（OR=0.685, 95%CI=0.654-0.718） and BMI (OR=0.961, 95%CI=0.935-0.987), and the use of endometrium preparation method (hormone replacement method, with ovulation cycle as reference) might lead to a lower live birth rate(OR=0.736, 95%CI=0.631-0.857). And the live birth rate was positively correlated with thicker endometrium (OR=1.058, 95%CI=1.024-1.094). The live birth rates of patients at 40, 41, 42, 43, 44 and 45 years old were calculated. It was found that the live birth rate was higher in BT group of different ages (P=0.024, 0.01, 0.198, 0.009, 0.102, 0.064), and the live birth rate gradually decreased with the increase of age. Conclusions: Single blastocyst transfer in elderly patients can achieve a similar live birth rate compared to double cleavage-stage embryo transfer, but twin delivery is lower.