Purpose: The purpose of this paper to explore a set of methods to formally display and analyze the nature and laws of the emergence and evolution of all kinds of medical collaborative practices (MCPs) within multi-level market.Methodology: Based on Yang’s neoclassical economics, the paper argues that the reason for the origin of MCPs with multi-level market is the division of labor for different medical services and medical transaction service. From an infra-marginal perspective, the study processes are (1) to build a role generation model for collaborators. (2) to determine the role boundaries of collaborators by calculating the corner solution, and formalize the entanglement between role identities and specific MCPs through the corner equilibrium analysis. (3) to evaluate the stability of different forms of MCPs by general equilibrium analysis, and analyze their possible evolutionary paths of various MCPs by sensitivity analysis of the stability conditions of different structures. Results: (1) A role generation model of "producer-consumer", which is composed of three functions and involves three economic parameters, reflects the coexistence of division and cooperation, and integrate the influencing factors with process views. (2) The paper extracts eight role models and six structures of MCPs with corner equilibrium, and further formalizes the different ways of legalization of specific role identities in different MCPs in no market, or single-level or multi-level market. (3) Three structures (structure A with no market, structure CN with single-level market and structure CC with two-level market) have global equilibrium in different parameter spaces. With the increase of learning cost of medical services and medical transaction services, there are two structural evolution paths more likely to occur: " A - >CN -> CC " and "CN -> CC ->A".Conclusions: The research will provide theoretical basis for the government to select, formulate and implement the relevant policies of specific MCP, and help IT companies better develop internet medical service transaction platforms.