In this paper, we discuss on accuracy of several kinds of power dissipation model for CMOS VLSI circuits. Some researchers have proposed several efficient power estimation methods for CMOS circuits [1][2][3][4]. However, we do not know how accurate they are because we have not established a method to compare the estimated results of power consumption with that of actual VLSI chip. To evaluate the accuracy of several kind of power dissipation model such as chip-level, block-level and gate-level etc., we examined as follows : (i) Measuring power consumption of actual microprocessors. (ii) Estimating power consumption with several kinds of power dissipation model. (iii) Comparing (i) with (ii). The experimental results show as follows: (1) Power estimation at gate level is accurate enough. (2) Estimating power of a clock tree independently makes estimation more accurate.