Based on the grey incidence analysis, the slope-incidence degree is modified and thus the concept of point-slope modification incidence analysis is deduced. Through the analysis of factors affecting air targets' attribute identification and combining the ideas of air defense by utilizing the grey point - slope modification incidence analysis and the multi-objective optimization method, this paper establishes a model of targets' attribute identification which can be used to effectively solve the complicated and difficult problem of targets' attribute identification by quantitative theory and also provides an auxiliary decision method for C31 system of air defense fight.