Abstract: Under the vertical structure of a single upstream producer and downstream oligarch competition, a dynamic game model was constructed about the upstream producers' differentiated manufacturing strategy and the downstream retailers' competition of double oligarchies. The effects of the upstream producers' differentiated strategies on their own enterprise profits and consumers' utility level were analyzed with or without the retailers' countervailing power. The results indicated that when the retailers don't have the countervailing power, the upstream producers tend to manufacture complementary products to improve their enterprise profits. When one of the retailers owns the countervailing power, the more complementary a product is, the greater the upstream enterprise's profiti is. In addition, the effects of product strategy on the consumer utility was studied when the retailers' countervailing power existed.