Aim: To evaluate whether using multiple displacement amplification (MDA) as the first step can increase the diagnostic efficiency of preimplantation genetic testing for monogenic disease (PGT-M) for β-thalassemia. Methods: This is a retrospective cohort study. All included patients underwent PGT-M cycles (n = 307) for β-thalassemia in our center from January 2014 to February 2018. We divided the patients into two groups based on two different detection methods. For the polymerase chain reaction (PCR) group (n = 115), multiplex nested PCR+ reverse dot blot analysis was performed directly after cell lysis. For the MDA group (n = 192), the whole genomes of single cells were directly amplified using MDA and then examined by singleplex PCR + reverse dot blot for β-thalassemia. Results: A total of 2315 embryos were tested. The overall diagnostic efficiency of the MDA group was significantly higher than that of the PCR group (96.99% vs 88.15%, P < 0.001). The percentage of embryos available for transfer was significantly higher in the MDA group than in the PCR group (74.28% vs 64.98%, P < 0.001). Furthermore, the carrier embryo rate of the MDA group was significantly higher than that of the PCR group (50.11% vs 35.95%, P < 0.001).Conclusion: This study indicates that MDA, as the first step in PGT-M for β-thalassemia, can increase diagnostic efficiency.