Evaluation is that a subject evaluates an object with certain value criterion, which is the premise and foundation of decision. The evaluating problem is becoming one of the popular issues in academe. In this paper, the essential meaning of evaluation is defined firstly, and evaluation process analyzed: putting forward the problem of evaluation; defining evaluation subject, evaluation organizer and evaluation criterion and method; processing and feeding back evaluation results. According to the essential meaning and process, the evaluation support system (ESS) is established, consisting of four function modules: problem definition module, data extraction module, mold database module and man-machine communication module. Based on the complexity of factual problem, the group evaluation support system(GESS) is established, which is an integration system of many valuators’ wisdom, experience and corresponding ESS. GESS is used to support group valuators to solve semi-construction evaluation problem on the basis of computer and network in order to acquire scientificity and objectivity in the evaluation of big system. Evaluation is that a a subject evaluates an object with certain value criterion, which is the premise and foundation of decision. The evaluating problem is becoming one popular problem in academe. In this paper, the essential meaning of evaluation is defined first, and evaluation processing analyzed: putting forward the problem of evaluation; defining evaluation subject, evaluation organizer and evaluation criterion and method; processing and feeding back evaluation results. According to the essential meaning and process, the evaluation support system (ESS) is established, consisting of four function modules: problem definition module, data extraction module, mold database module and man-machine communication module. Based on the complexity of factual problem, the group evaluation support system (GESS) is established, which is an integration system of many valuators’ wisdom , experience and corresponding ESS. GESS is used to support group valuators to solve semi-construction evaluatio n problem on the basis of computer and network in order to acquire scientificity and objectivity in the evaluation of big system.