Context The timing of early cumulus cell removal (ECCR) can be changed within a range. The change has an effect on the multiple pronuclei (MPN) rate and the exposure time of oocytes to sperm waste products. The timing of ECCR effects the outcomes of assisted reproductive technology, however, it is still unclear what time is best for ECCR. Aims To find the best time for ECCR based on clinical outcomes in order to increase the success rate of assisted reproductive technology. Methods A retrospective study was performed. Cycles were categorised into six groups according to the timing of ECCR. The clinical outcomes of these six groups were compared by Kruskal-Wallis test and Pearson X 2 test. Key results The timing of ECCR had a significant effect on the MPN rate, 0PN without cleavage rate and grade 1-2 embryo rate at Day3. Among our six time groups of ECCR, the cumulus cell removal ≤4h post-insemination group had the highest MPN rate and grade 1-2 embryo rate at Day3, and the 5.5h<time≤6h group had the highest pronuclear formation failure rate. In addition, 2PN rate was not significantly different among the six time groups. Conclusions Within the time range of ECCR in our study, selecting an earlier timing to remove the cumulus cells may have a better outcome. Implications ECCR is helpful for optimisation of the short-term insemination strategy.