The combined effect of indole-3-acetic acid and mepiquat chloride on the endogenous gibberellins of aerial and underground tubers as well as tuber yield was studied on Chinese yam plant. Two plant hormones were combined in the following concentrations: IAA 50, 100, 200, and 300 ppm, plus MC 600 ppm. Combined plant hormones were foliar-sprayed once in early July. Exogenously applied IAA combining mepiquat chloride increased fresh weight of the aerial and underground tubers affecting the increase of endogenous gibberellins. The results suggest that IAA is likely to be one of the active plant hormones responsible for aerial tuber growth and enlargement, stimulating the promotion of endogenous gibberellin when combined with mepiquat chloride.