中文摘要：

对企业可抵押资产规模、信贷市场类型与中小企业融资的关系问题进行了研究．在道德风险框架下，考虑到企业可抵押资产规模，针对垄断性和竞争性借贷市场分别构建了相应的抵押贷款模型，并刻画了最优合约的特征．结果表明，银行收益不仅受信息结构的影响，同时还受到企业可抵押资产规模与信贷市场结构的制约．进一步地，在垄断性借贷市场中，可抵押资产存在一个临界阈值，低于该阈值的企业将面临信贷配给．而在竞争性借贷市场，银行会降低对于企业的抵押品要求，从而使中小企业融资难问题得到缓解．最后，对于当前中小企业融资难问题提供了理论解释和启示．

英文摘要：

This paper puts focus on how small and medium-sized enterprises （SMEs） financing is influenced by client firms＇ assets size and credit market type. By taking account of firms＇ assets size, we develop two moral-hazard models under monopolistic and competitive credit markets respectively, and then characterize the optimal contract. The results show revenues of the banks are influenced by not only information structure but also firms＇ assets size and credit market type. Furthermore, the results indicate there exists a threshold value of mortgage assets under monopolistic credit market ： when firms＇ mortgage assets are lower than this value, credit rationing is implemented by the bank. However, banks have to lower their requirements of mortgage assets in competitive credit market, and this contributes to relieving SME financing problem. Finally, some suggestions are given to overcome the difficulty in providing financial services to SMEs.