Abstract: The combination of finance and the entity economy is the main trend of the "new normal" period of Chinese economy, and thus the equity investment industry has been vigorously supported by the policy. In addition to lack of funds, the development of business entities can do nothing without the support of supply chain, and it will be affected by the cooperation mode between the supply chain enterprises. Therefore, when financial institutions make equity investment to enterprises, they begin to consider the influence of supply chain, to consciously make acquisitions, mergers and even to build upstream and downstream to reduce the friction between the supply chain enterprises, and to accelerate the development of financing enterprises. However, this behavior is always costly, and the operation and market risk is completely borne by the investment and financing parties. The efficiency of the allocation of financial resources is reduced. Based on the realistic background, the impact of supply chain contract on the equity financing of growing retail enterprise is studied in this paper. It is assumed that the investment institution (in this paper, a private equity investment institution, PE,is considered) adopts P/B method (with P/B ratio as α) to valuation the retail enterprise, and the investment volume is B. The retailer holds a fixed asset A and own fund η, and then his stock share becomes to θ=(α(A+η))/(α(A+η)+B) after equity financing. It is considered that the retailer faces a random market demand ξ, where only the mean μ is known to him. With the help of equity financing, the retailer could expand the market demand from ξ to ξ+βe, where β represents the retail enterprise's growth-potential, and e represents the retailer's sales effort. The effort cost function is expressed as 1/2 se², and retailer's selling price is p, and the supplier's unit cost is c. The Stackelberg version of the problem with the supplier act as the leader is explored, then the retailer needs to decide the optimal order quantity q to maximize his expected total asset TA_R=θ(A+η+B+pmin{q,ξ+βe}-wq-1/2 se²) after the supplier chooses optimally the selling price w, which maximizes the supplier's profit function π_s(w)=(w-c)q. Since the demand information is incomplete, a minimax regret criterion is taken to solve the optimization problem. Under two kinds of different supply chain contracts, the supplier and retailer's optimal decisions are obtained. It shows that the retailer's equity financing is greatly influenced by the contractual structure. On the one hand, the supplier-dominated contract structure seriously impedes the retailer's equity-willingness, and is not conducive to the development of enterprises. On the other hand, through a kind of contract locking protocol, the equity-willingness of the retailers can be improved and the win-win situation can be achieved. It reveals the significance and value of a reasonable settings of supply chain contract structure in the process of equity financing.

Key words: contract structure, supply chain, equity financing, equity-willingness