Objective: To evaluate the effect of transferring a poor quality embryo (PQE) with a good quality embryo (GQE) on the outcomes in poor prognosis patients. Design: Retrospective cohort study. Setting: University-affiliated hospital. Population: A total of 5,037 FBT cycles between January 2012 and May 2019. Methods: Single FBT with GQE were defined as group G and double FBT with GQE plus PQE were defined as group GP. Propensity score matching was applied to control for potential confounders. Multivariate generalized estimating equations (GEE) models were used to identify the association between the effect of an additional PQE and outcomes. Main Outcome Measures: Live births and multiple pregnancies. Results: Group GP resulted in a significantly higher live birth rate (LBR) than group G in women aged 35 and over and in women who received over 3 cycles of embryo transfer (ET) (48.1% vs 27.2%, OR:2.56, 95% CI: 1.3-5.03 and 46.6% vs 35.4%, OR:1.6, 95% CI: 1.09-2.35), while LBR were statistically similar between two groups in women under 35 and in women who received less than 3 cycles of ET (48.7% vs 43.9%, OR:1.22, 95% CI: 0.93-1.59 and 48.3% vs 41.4%, OR:1.33, 95% CI: 0.96-1.85). Notably, group GP were found a consistent significantly higher multiple pregnancy rate than group G. Conclusions: The transfer of an additional PQE with a GQE increases live births in poor prognosis patients. Funding：None. Keywords: poor quality embryo, good quality embryo, LBR, poor prognosis patients