With the emergence of Web 2.0, people start to share their life stories, photos, videos, or even knowledge on the web. Wikipedia (http://en.wikipedia.org) is a well known web site where people can contribute and share their knowledge. Wikipedia provides a knowledge sharing platform to the knowledge providers who are willing to share their domain knowledge to and have interaction with others. However, Wikipedia can only help the knowledge providers to share their knowledge. Most activities and functions on Wikipedia are supported for the knowledge providers but few for knowledge demanders. In addition, there have been many knowledge services emerged on the Internet. The existing types of knowledge services provide the platforms to match the knowledge seekers and solvers, but they are passively waiting for the appearance of solvers. We propose a mechanism of knowledge service on Wikipedia which provides expert identification and expert matching functions to actively inform potential knowledge providers. In order to support the proposed knowledge service, we further propose a knowledge activity map system to present a Wikipedian’s knowledge activities, such as editing on Wikipedia. This research focuses on the development of knowledge activity map system and the evaluation of feasibility of proposed knowledge service on Wikipedia. The experimental results show that the proposed knowledge service is feasible on Wikipedia, but the capability of knowledge activity system needs to be further improved to increase the quality of the proposed knowledge service.