This paper proposes a method which composes document services over the Internet automatically based on multi-agent and semantic technology, and discusses the implementation of three document service functions (catalog browsing, document information browsing and document full version downloading) with that method. We use service delegate agent to encapsulate services on the internet; use service purchase agent to decide which service delegate agents should be used and then to generate a composition script describing how these services being purchased should be used; use service provider agent to call these services according to the composition script and merge the results, translate the merged result into the system predefined format, finally return it to the requesting user. By doing so, service provider can simply composite existed services on the internet and provide full functional service.