Abstract: Adopts Post-Chicago School’s definition of monopoly,this paper designs a consumer demand function based on Logit model,computes the market performance of differentiated products firms merger by a numerical simulation approach,finally tests the whole evaluation process by a group of simulated data.The result shows that merger which induces concentration soaring wouldn’t raise price level,meanwhile, sharply increases post-merger firm’s profit and competitiveness for the reason of marginal cost reduction.Consequently,such merger is harmless to consumer and doesn’t give rise to monopolistic effects.

Key words: differentiated products, Logit model, market performance