Abstract: Is the institutional convergence of non-profit arrangements in the elderly care service the result of what economists call the "efficiency" triumph? Using the new institutionalism theory of organizational sociology to analyze the choice of the form of elderly care service organizations under the changes of the system and market environment, the study found that the pursuit of legitimacy of elderly care service organizations shows a higher tendency to institutionalize, and at the same time, it plays a logical role in strengthening the welfare system. Under the circumstance, non-profit organizations are rapidly spreading and occupying a leading position in the emerging middle and low-end elderly care services through the “externalization” strategy. In the process of proliferation, the degree of "separation" of appearance began to converge, but more hidden "joint-enterprise-type" non-profit elderly care service institutions appeared. The new externalization model is driven by the habit of "economic man" and is a product of adapting to the new institutional environment under the logic of a strong welfare system. Finally, it is recommended to strengthen supervision and regulation of non-profit elderly care service institutions, and conduct classified management of organization service outsourcing.

       Key words: Institutional Environment; Non-profit Elderly Service Organizations; Externalization