In recent years, in order to avoid the risk of default, in general, banks take stringent mortgage credit to SMEs who are inadequate information, high credit risk in China, and SMEs involved in the credit market generally are restrained by the lack of the mortgage assets. This article attempts to set up credit model of SMEs, and argues that the view innovation of mortgage assetst and the reputation mechanism will encourage enterprises to honor the contract, and the credit risk will be reduced.