This thesis is based on the theory of Transaction cost to analyze the problems of transaction cost in the internal market of computer product channels.Computer product distributors are as the selected our main research target to analyze the effect of their transaction cost and their strategies when facing the cooperation relationship between the up- stream suppliers and down- stream retailer. This thesis uses multiple case study as research methodology, selecting five representative distributors, such as Acer Inc, Synnex technology international corp. , Gemuine C&C Inc., Xander international corp. and Taiwan aries corp. LTD., etc. To proceeding analysis and interview. The research results obtained show that computer product distributors have to assist up- stream manufacturers to solve the problems of transaction cost not only between retailers and customers but also between themselves and down- stream retailer and even between customers at end-point. In the other hand, as their competition strategies, it¡¦s necessary and important to pay attention on problems of transaction cost between up- stream manufacturers, management of possible conflicting channels and the fierce competition at this area. Therefore, computer product distributors must use relative channels carefully to solve the problems of transaction cost between manufacturers, retailers and customers.