Abstract: When multi-product and the network externalities exist, how to set a reasonable price to gain maximum profit for a monopolist is a major issue for urgent solution. Through setting a two stage-game dynamic model with perfect information, the paper researches the pricing strategies for a monopolist with network externalities and multi-product in two-period sales. The results show that the stronger the network externalities, the lower the first-period price is and the higher the second-period price is. The optimal price getting from two-period sales integrally is lower than the price getting from two-period sales separately.