Abstract: According to the requirement of floorplan-based analysis and optimization of power networks, an approximate circuit model of VLSI power networks was presented in this paper. Power networks were divided into two levels in response to their structural features, and then circuit models of their components were built considering statistic character of drain currents distribution of standard cells and reduced with Norton equivalent circuits. Experimental results show that analysis result of the proposed model is less than that of pessimistic analysis, which is 38.75% (the worst voltage drop) and 36.04% (voltage drop of center node) respectively.