Objective To explore the possible mechanism of human adipose-derived stem cells (hADSCs) promoting seawater immersion wound healing in vitro. Methods Human epidermal cell line HaCaT cells and artificially simulated seawater were used to establish an in vitro model of cell damage induced by seawater immersion. hADSCs were isolated from human adipose tissues, and a co-culture system of HaCaT cells and hADSCs was established. The proliferation and migration abilities of HaCaT cells were detected by cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) cell proliferation detection kit and cell scratch test. The activation levels of epidermal growth factor receptor (EGFR)/extracellular-regulated protein kinase (ERK) signaling pathway were detected by Western blotting and real-time quantitative PCR. Results The proliferation of HaCaT cells cultured with the medium containing 10% artificial seawater was significantly inhibited compared with the cells cultured without artificial seawater (P<0.05). The proliferation and migration abilities of seawater-cultured HaCaT cells were significantly lower than those cultured without seawater and those with hADSCs and seawater (all P<0.05), but there were no significant differences in cell proliferation or migration abilities between the HaCaT cells cultured without seawater and those co-cultured with hADSCs and seawater (P>0.05). The expression of EGFR/ERK signaling pathway in seawater-cultured HaCaT cells was significantly inhibited compared with the cells cultured without seawater and those co-cultured with hADSCs and seawater (P<0.05), while the expression of EGFR/ERK signaling pathway was not significantly different between the HaCaT cells cultured without seawater and those co-cultured with hADSCs and seawater (P>0.05). Conclusion Seawater can block the activation of EGFR/ERK signaling pathway and inhibit the proliferation and migration of HaCaT cells. hADSCs can promote the activation of EGFR/ERK signaling pathway and reduce the inhibition effect of seawater against proliferation and migration of HaCaT cells.