The communication between the teachers and students is very important in network education. Question-answering system can resolve the problem. This paper proposes a question answering system in network education based on FAQ and then introduces the kernel module which is the calculation of the question similarity in detail. The paper presents the similarity algorithm of domain keywords and common words respectively and integrates them into the question similarity. Experimental results show that the proposed method can achieve good performance and the system is applied.

When using natural language question to retrieval document, query expansion are the key factors that affect its retrieval performance. By analyzing the traditional query expansion method, this paper puts forward a query expansion method based on set theory for answering document retrieval. In order to verify the validity of the method, a similarity calculation method for question and candidate answer sentences is proposed to extract the answer. The major query expansion terms and the minor query expansion terms are taken into consideration with different weight in the similarity calculation. The experiment results show that the performance makes substantial improvement.