In this paper, we build a partial equilibrium model to explore a downstream firm's outsourcing decision in the final goods market by utilizing the assumption of outsourcing costs in Shy and Stenbacka (2003). First, we discuss a monopolistic downstream firm's decision of outsourcing in the final good market. Then we extend the model to a duopolistic downstream market structure with two competing firms to examine whether the outsourcing decisions change in such a competitive environment. It is found that, when the final good market structure is monopoly, no outsourcing occurs under that both the upstream firm (i.e., the outsourcing service provider) and the outsourcing firm incur the same fixed cost. This is because the revenue the upstream firm earns is not sufficient to cover the fixed cost of setting up a manufacturing factory such that outsourcing is unprofitable for the upstream firm even when the downstream firm has an incentive to outsource. Nevertheless, outsourcing does occur if the downstream market appears to be competitive. In this case, there exist two effects: one is that, due to the market competition, the duopolistic downstream firms' market shares and their revenues decrease, thereby lowering their ability to burden the fixed costs of setting up a manufacturing factory; the other is that the increasing demand for the intermediary goods from the downstream firms raises the upstream firm's incentive to accept the outsourcing contract. This article main discovery ever the upstream firm does not have the advantages of product cost, as long as the final goods firm facing more competes to the market, possibly causes outside the committee the production situation occurrence, i.e. the market competition degree carries on outside the committee for the firm the generation of labor cause and motives one.