Based on the discussions of the origin, development, advantages and disadvantages of OEM, this paper makes a theoretical and empirical study on OEM with game theory models, which is concerned and discussed by entrepreneurs and economists. The following conclusions have been testified: (1) The export price of OEM products keeps descending as the number of firms increases, and when the number becomes large enough, the price will approach the product cost of domestic firms;(2) The more domestic firms do OEM, the more profits foreign firm will get; (3) When there is only one domestic firm doing OEM , that is at a monopoly position, it will get the maximum profits; When there are two, the their total profits will be about the same as those of the foreign firms; But when the number of domestic firms is over two, all the profits of these firms will be less than those of the foreign firms.