SMEs financing difficulty is a problem that needs to be solved urgently. This paper points out that the introduction of policy-related guarantee institutions is an efficient solution to SMEs financing difficulty. It firstly builds a three-party theoretical model connected with policy-related guarantee institutions, commercial banks and SMEs, and creatively copes with the matching of risks and revenues through options combination strategy. Then it employs numerical simulation methods to analyze the feasibility of the guarantee of SMEs loans by policy-related guarantee institutions in the aspects like scenario analysis and breakeven calculation. It arrives at the following conclusion that in most cases, it is feasible that policy-related guarantee institutions provide the guarantee of SMEs loans. In addition, it also shows that under marketized guarantee industry, SMEs financing costs significantly decrease compared with current constraints. It argues that based on the accelerated advance of marketization orientation in guarantee industry, the guarantee of SMEs loans by policy-related guarantee institutions under options combination mechanism is a solution to SMEs financing difficulty.