Based upon the view that changes in institutional environment have an effect on transaction attributes, which will make anew the choice of economic organization, the purpose of the thesis is to explain the organization development and structure change of Mainland China's non-state-owned enterprises. It tries to modify O. E. Williamson's theory of governance structure in order to theorize China's economy more suitably. More importantly, the thesis describes a specific dimension of transaction ¡Ðthe need for "political reliance" in the transitional economy, with which we supplement and/or on substitute Williamson's (1999) concept of "probity". We find out that the need for political reliance in stead of probity, is the key to understanding why and which kind of governance mechanism is more "efficient" in managing transaction in Mainland China's non-state-owned section. The theory we establish is applied to explaining the organization development and structure change of Mainland China's non-state-owned interprises, which have experienced different need of political reliance in different stages of China's economic reform. Especially suitable for the theory to explain is about the surge and fall of the unique form of organization, i.e. the so-called "Gua-kau"(±¾¾a) enterprises. The thesis also predicts the tendency of structure change in Mainland China's non-state-owned seitor by using the same theory.