The aim of this study was to explore the mechanism underlying the promotive effect of morroniside on rat mesenchymal stem cell (RMSC) proliferation and to provide an experimental basis for the development of potential new drugs. RMSCs were obtained from the bone marrow of Sprague-Dawley rats aged 3-4 months. The proliferation of primary and subcultured RMSCs in the high‑, medium‑ and low‑concentration morroniside intervention and blank control groups was observed using light microscopy. Cell proliferation and survival conditions were detected using methyl thiazolyl tetrazolium (MTT) colorimetric tests. Light microscopy and the MTT assay revealed that RMSC adherence time in the morroniside groups was shorter compared with that of the control group. Twelve hours after the media of primary RMSCs were changed, the number of adherent cells in the morroniside groups increased and an elongated cell morphology was observed. The cells at the fourth passage in the morroniside groups fused completely 12‑16 h after inoculation and then rapidly entered into the logarithmic phase. The primary RMSCs of the morroniside intervention groups grew into typical bone marrow mesenchymal stem cell (BMSC) colonies after 4 days of morroniside treatment and their fusion rate had reached 80% after 9‑11 days. By contrast, the cell fusion rate of the control group only reached 75-80% after 14 days of morroniside treatment. Morroniside exhibited a similar promotive effect on proliferation in primary and subcultured RMSCs. Morroniside may promote RMSC proliferation through secreted factors, cell-to-cell interactions and/or the interactions between cellular adhesion molecules and extracellular matrices (ECMs). However, the specific mechanism underlying this effect remains to be fully elucidated.