In this paper, we develop a Vietnamese Question Answering system to answer simple questions about provisions, processes, procedures, and sanctions in law on enterprises Vietnam. Research to build a Vietnamese Question Answering system is more difficult than English Question Answering system because of lack of Vietnamese processing resources and tools, or their results isn’t high. We have utilized available Vietnamese resources, tools and modified some tools (such as Lucene) and algorithms, which worked well in English, applies in Vietnamese. From that, we have proposed a similarity-based model to build a Vietnamese Question Answering system in Vietnam’s legal documents, namely vLawyer system. In experimental section, we achieved promising result, about 70% precision in legal documents, it proved that our approach is reasonable in legal document domain.