Abstract: With the increasing popularity of online advertising, the choice of appropriate online advertising has been the key of successful publishing. Enterprises are faced with dilemma when they select the investment between the portal online advertising and the long tail online advertising. Presently, however, there are no theories and methods aim to the portal online advertising and the long tail online advertising for publishing. Therefore, it is urgent to cry for the theories, methods, and models of online advertising publishing to instruct effectively the operation and management and create more value for enterprises. In this paper, Cobb-Douglas sales function S（a，q）=α-βa^-γq^-δ is introduced and non-cooperative static Nash investment model, cooperative static Nash investment model and Stackelberg investment model with game theory are built based on the portal online advertising and the long tail online advertising, through the analysis of model equilibrium to get the conditions that advertising investment gain big return from a small investment. In the condition of Stackelberg game model, the conditions are obtained that the long tail online advertising get big revenues from a small investment and the portal online advertising get big revenues from a small investment when they are successively invested respectively. Compared Stackelberg Equilibrium with non-cooperative Nash Equilibrium, the prior investment of online advertising gets big revenues from a small investment and subsequent investment gets small return from a big investment, and the relation of total investment and profits are uncertain. Compared with the non-cooperative online advertising investment model and Stackelberg game online advertising investment model, only the advertising investment based on cooperative Nash Equilibrium strategy can get the maximum profit. Furthermore, it verifies the validity of conclusion with a numerical example. The study conclusions solve dilemma for enterprises when they are faced with the investment between the portal online advertising and the long tail online advertising, it also provides enterprises a new theoretical basis and decision-making method for online advertising investment.

Key words: portal online advertising, long tail online advertising, Stackelberg game, Nash Equilibrium