Pro bono service（or professional volunteer service）is the donation of professional services to social organizations. It has emerged and been popular recently both in China and abroad. These volunteers are mainly professionals from enterprises，with technological skills or management experiences. The professional volunteer services that they provide include project consulting，human resources management，financing，IT and etc. In the light of its characteristics of providing professional services oriented to social organizations，pro bono may become a new and effective way to support capacity building and sustainable development of social organizations. Due to the lack of research in this field，the thesis attempts to introduce and preliminarily explore the subject，by briefly discussing the concept of pro bono，its emergence and growth in China and other countries，analyzing a few specific cases，expounding the significance of volunteer services and the challenges faced during its growth. Finally，the thesis gives a few suggestions concerning the development of pro bono service for social organizations in China.