Equity financing has become an important financing channel for enterprises to seize market share and achieve leap-forward development in market competition. The formulation of financing decisions must consider the competition behavior among enterprises in the product market. The paper constructs an equity financing model considering market competition for duopoly retailers,and investigates the mechanism of the competition for equity financing decision when one of the retailers adopts equity financing for market development.Results show that the retailer's equity financing should consider the direct and indirect effects of market competition under different retailer growths; market competition inhibits( promotes) equity financing of low-growth( high-growth) retailers. When the supplier participates in the game,the retailer's financing strategy depends on the trade-off between market competition and market development under different initial market sizes and growths.