The article investigates the function of non-financial service intermediaries in informal financial network for middle and small business financing. It shows that long-term service intermediaries can facilitate middle and small businesses accessing to financing through their good informal cooperation relationship with the lender. The service intermediaries, such as lawyers accountant, managerial consulter, provide not only professional service but also aid in financing, therefore contribute to resolving the jam of middle and small business finance. This analysis provides a theoretic foundation for enacting the correlative policy.