Abstract: In this paper，a Q&A system structure based on CBR technique is proposed.A CBR brief introduction is given at first.And then the plan of the Q&A system structure is provide.In the third section，after presented case-database structure，case-weight definition and determination is explained.In the end，steps and formulas used in the system is put forward.The remedial measure is given in case of system invalidation.Compared with traditional mode，the system supported in this paper is more accurate and efficient.

摘要： 提出了一种基于案例推理技术的网络教学平台答疑系统的结构。简要介绍案例推理技术及其关键技术，然后给出了答疑子系统的结构设计图，并对设计图的各个模块进行了简要说明。对案例库的构建及案例权重的定义和维护进行了详细的说明，并给出了权重维护的步骤及公式。最后，系统给出了检索案例失败时的补救措施，即通过传统答疑方式，由专业教师给出解答，并添加案例致案例库。该系统较之传统答疑方式在答疑效率以及资源重用等方面有较大改进。