Referring to value engineering expression F = C /T,this paper builds the value formula V = F /CT by adding time factor T. According to the connotation of F,C,T,value formula is expanded into three- level index system. Enterprise diagnosis can be accomplished through sorting of weighted gap between the third level indicators and the optimal level in the same industry. The V value calculated is the enterprise value evaluation. Value formula,organically integrating of diagnostic tools and enterprise value evaluation tools,has strong theoretical value and practical significance. An application of value formula in one high- tech enterprise is given at last.