In response to the proposal of a development goal in 2006 to establish China into an innovation-oriented country, a package of innovation policies have been promulgated, playing a significant role in supporting the future science and technology development in China. As an important part of national innovation system, high-tech zones serve as both an implementer of central policy and a maker of local policy. It is noted that many policies made or implemented by high-tech zones are of experiment. Previous study shows that policy experimentation is more likely to occur in centralization than in decentralization.(Cai &Treisman 2007). From China’s economic reform experience over the last three decades, it can be found that formulation and implementation of any macro-policy in China have gone through policy experimentations (Heilmann, 2008). Helimann proposed a pattern of central-local interaction to generate policy---“experimentation under hierachy”. To his belief, China’s policy experimentation is under control of central government. Helimann’s conclusion overlooked the  local government’s initiative. Based on the literature review and the case of Zhongguancun through a try to analyze the mechanism of innovation policy experimentation, the paper proposes the concept of a middle-diffusing type of policy experimentation. The main finding is that with the deepening of science and technology system reform, it is local government who initiates policy experimentation, playing the role of “a primary acting group".   China’s local government, with the motivation to be a “bellwether” among its counterparts, strives to collect policy demands from enterprise and research institutions, and obtain support from its central government.