This paper take enterprise's collective brain drain as the research object, by using of questionnaire method, historical data, experts consultation method, and other methods of construct the collective brain drain of forewarning indicators, and then use the alternative ranking method to determine and evaluate comprehensively system of indicators to the weight. By constructing the forewarning system to real-time monitor, identify, diagnose and evaluate the trend of enterprise's collective brain drain and on this basis to pre-control, the prior development of corrective measures, the crisis will be resolved in the embryonic stage. Therefore, constructing the forewarning system of enterprise's collective brain drain for the long-term stable development of enterprises has important practical significance.