Abstract:    The science and technology (S&T) plan is the main way for the government to allocate S&T resources and organize S&T activities, which has a far-reaching impact on China′s S&T development. Considering comprehensively the major historical events, this paper takes the previous S&T plans since 1949 as the research object and studies their evolution laws. 
Based on the punctuation-equilibrium framework in the policy process theory, combined with the Chinese situation of S&T planning, this paper puts forward an analysis framework of S&T plan evolution which takes the S&T development outlook as the core. The S&T development outlook include S&T plan goals, intellectual policy and S&T development concept in a specific period. Generally, the S&T development outlook are stable, and only when major changes occur will they affect the policy landscape. First, the S&T development outlook have not changed, the policy landscape is relatively stable, the policy is implemented within the original framework and forms a policy monopoly, which reflected an equilibrium period. Second, the S&T development outlook have changed, but their changes can′t promote the new policy landscape to replace the old. The policy is gradually adjusted to reflect the new S&T development outlook, which reflected an equilibrium period. Third, the S&T development outlook have changed, and their changes have led to the replacement of the policy landscape, the change of policy field, and the break of policy equilibrium, which reflected a punctuation period.
    Based on the S&T plan evolution framework, the paper summarizes the punctuation and equilibrium features of previous S&T plans, emphatically analyzes the policy landscape and policy field affecting the equilibrium period. It is found that China′s previous S&T plans show obvious characteristics of alternation of equilibrium period and punctuation period. There are not only policy punctuation periods under major events, but also policy gradual adjustments and policy monopoly in the equilibrium period. First, the S&T development outlook is an important policy landscape affecting the evolution of S&T plans, and the key to determine whether S&T plans are in a state of policy equilibrium in a long time. Second, the change of policy landscape is basically consistent with the punctuation equilibrium evolution process of S&T plans. The S&T plan goals, intellectual policy and S&T development concept constitute the policy landscape in different periods. Third, the policy field has gradually formed a mechanism with diversified participants and democratic decision-making in the evolution of S&T plans.
   At the same time, this paper further puts forward some suggestions to carry out S&T plan research from the perspective of policy process.

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Key words: S&T plan, policy evolution, punctuation-equilibrium