Since 2006, China is undergoing a rapid growth in social work. In contrast with the rapid expansion of the scopes and fields for social work, the need for specialization in social work is creasing. Especially in mental health service in community, this demand is even higher. This article is intended to study a project on mental health in community called Assertive community treatment carried out in Shenzhen for 4 years, and finds that: a) the longstanding accompanying service is different from the short-term services; b) the longstanding accompanying service is another kind of specialized social work; c) the longstanding accompanying service is the best way for Chinese social workers to promote specialization of social work.