Abstract: In enterp rise merger, if the buyer and the seller make reasonable evaluation on the value of objec2 tive enterp rises, the transaction can be made. The value of an enterp rise is cap italized for expectation gain, and the key to evaluation of the value of an enterp rise is to accurately evaluate the expectation gain of the enterp rise. By u2 sing random variables to rep lace expectation gain, theoretically, it is feasible to solve expectation function but in p ractice, its accuracy is not high. In order to solve this p roblem, Alfred put forward RappaportModel to calculate all kinds of future years cash flow of the enterp rise and used weighted average cap ital cost to obtain the value.