This paper emphasizes the irreplaceable role that plays the basic medical insurance in the aspect of input-output ratio of fairness based on the theoretical and practical data analysis. The basic medical insurance has been in instrumental action and must continue to play the core basic role, while the commercial insurance should play the supplementary role. From the perspective of the insurance content, the basic medical insurance "guarantees the basic health needs" and the connotation of "basic insurance" is to guarantee the medical expenses in the catalogue of basic medical insurance, which should conform to the principles of clinical necessity, safety, effectiveness and economy. Medicines, services and facilities which are not registered with these principles in the basic medical insurance catalog can be regarded as "non-basic", and thus be excluded from the basic need guarantees to be provided with residents. Commercial insurance and basic medical insurance should complement each other to ensure residents are provided with differentiated and high-level service needs, which can realize effective connection. In this new era, the gap between available funds and the demands of basic medical insurance can only be bridged by improving the treatment combination mode and the financing mechanism of urban-rural medical insurance for residents.