| On the condition of cybereconomy, the contents of spatial knowledge flow have changed to a certain extent, which makes the study related to knowledge spillovers vulnerable, cause the contradiction between the theory of knowledge flow and its practical development.Based on the definition of the knowledge flow and the spatial distribution of innovation activities, a conceptual model reflecting knowledge flow and a spatial dynamic general equilibrium model on regional flow are constructed. This paper discusses the regulations of knowledge flow features under the condition of cybereconomy theoretically, and then unfolds the evolution mechanisms of innovation activities geographically.First, on the basis of the definition of the distribution of innovation activities, the paper uses the index of spatial distribution measures to describe and analyse the distribution of American innovation activity and its changes over time on the state level. The results showed that: from 1963 to 1999, GE (0) index, GE (1) index, Gini coefficient and E-G index, the innovative activities spatial agglomeration were relatively consistent first, and then decline after the rising trend; and the Moran's I index demonstrated that the spatial agglomeration degree experienced a gradual decrease trend, meant that central area of innovation activities in space presents on a scattered trend year after year.Second, after clarifying the concept of the knowledge flow, this paper identified the main approaches and impact factors on knowledge flow. Based on Meusburger's model, a qualitative model reflecting knowledge flow is built to reflect its new characteristics under cybereconomy. Here we choose the United States as the sample, the patent citation data from a large time span are used to verify knowledge flow characteristics spatially and their trends. The results confirmed the deduction based on the model built, meant that two characteristics present a weakening trend as time went on, but the impact of space on knowledge flow does not disappear completely.Third, this paper revises the Richard Baidwin model of localization spillover, and analyse the long-term equilibrium state on condition of knowledge flow degree, and demonstrates the mechanism on spatial distribution of innovation activities through the dynamic simulation. The results of the study indicates that knowledge flow is the force to promote the scattering of innovation activities; the increase of trade freedom through this process has played a reverse role, which is the strength to promote the spatial agglomeration of innovation activities; distribution of innovation activities and expend exist positive synergy effect; the increasing of trade freedom made the long-term equilibrium evolution trend caused by increasing knowledge flow takes on much diversification.Fourth, on the basis of characterizing the spatial distribution of American innovation activities and knowledge flow on a cross-states level, from two dimensionalities—the whole United States and representative regions, this paper discusses the influence on different dimensions of overall regional innovation distribution and regional innovation share on the high, medium and low level made by knowledge localization and also the two kinds of typical knowledge flow. This paper also examines the spatial distribution effect of innovation activity with knowledge flow; and consummates the theoretical research on innovation activities spatial distribution of knowledge flow. The research has confirmed several assumptions related to the innovation activities spatial distribution effect of knowledge flow, and it also shows that: the effect of localization flow on spatial distribution isn't significant; knowledge inflow characterized with patent citing and outflow characterized with patents cited made obviously difference on the the share of regional innovation, and the former improving the share of regional innovation, while the latter reducing it.
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