政府向社会组织购买公共服务是提供公共服务的一项主要途径，也是当前提高公共财政使用效率、创新管理体制改革的重要措施。十八届三中全会以来，我国政府不断聚焦政府职能转移，逐步探索向社会力量购买公共服务，利用市场和社会力量来提高公共服务供给的数量与质量，实现政府职能转移。社会工作机构作为社会组织的一种重要组成形式，承接了大量社会公共服务，在推进政府职能转移、社会治理创新方面，发挥了十分重要的作用。

本文以北京市C区政府购买社工机构服务为例，以资源依赖理论、合作治理理论、公共价值理论为基础，通过质性研究的方法，对参与过C区政府购买社工机构服务的相关人员进行半结构式访谈，在文献与访谈资料的支持下，详细了解C区政府购买服务的政策依据、购买流程、参与主体，以及不同主体承担的角色和发挥的作用，试图发现政府与社工机构的互动机制，探索构建互动模型。研究发现，C区于2009年设立了专项资金，通过购买服务的方式，支持社工机构参与社会建设工作，参与主体主要包括政府、社工机构、服务对象、评估机构，政府占主导地位。目前存在政府资金不稳定、双重角色叠加，社工机构独立性不足、人员流动大、专业性不强，服务对象参与意识不强，评估机构不够客观中立等问题。为了构建四元主体间平等合作的互动关系，政府要不断完善政策制度，社工机构要切实提高自身能力建设，服务对象要积极参与社会治理，评估机构要提升评估专业性和实用性。

The government's purchase of public services from social organizations is a major way to provide public services, as well as an important measure to improve the efficiency of public finance and innovate the management system reform. Since the Third Plenary Session of the 18th CPC Central Committee, the Chinese government has been focusing on the transfer of government functions, gradually exploring the purchase of public services from social forces, using market and social forces to improve the quantity and quality of public service supply, and realizing the transfer of government functions.As an important form of social organization, social work institutions have undertaken a large number of social public services and played a very important role in promoting the transfer of government functions and innovation of social governance.

Based on the theory of resource dependence, the theory of cooperative governance and the theory of public value, this paper takes the purchase of social work services by the Government of C District in Beijing as an example, to conduct semi-structured interviews with relevant personnel who have participated in the purchase of social work services by District C government, supported by literature and interview data, in order to find out the interaction mechanism between the government and the social work organizations, we should have a detailed understanding of the policy basis, the purchasing process, the participants, and the roles and roles of the different actors in the service purchase of District C government, explore building interactive models. The study found that District C set up a special fund in 2009 to support social work organizations to participate in social construction by purchasing services, the main participants include the government, social work agencies, service objects, evaluation agencies, the government-dominated. At present, there are some problems, such as the instability of government funds, the superposition of double roles, the lack of independence of social work organizations, the great mobility of personnel, the weak professionalism, the weak sense of participation of service clients, and the lack of objectivity and neutrality of evaluation organizations. In order to build an interactive relationship of equal cooperation among the four subjects, the government should constantly improve the policy system, the social work institutions should improve their own capacity building, and the service objects should actively participate in social governance, evaluation agencies should enhance the professionalism and practicability of evaluation.