Abstract: According to the power consumption of 2.4 GHz active RFID tag,the paper proposes a dynamic frequency modulation low power design method.Tag uses NXP's LPC1758 MCU and TI's CC2520 RF chip.The frequency is controlled by changing CPU clock source,configuring PLL value and CPU clock frequency divider.Tag adjusts the CPU clock frequency adaptively according to the characteristics of the code fragment operation.It is found that the power consumption on standby of the tag of dynamic frequency CPU is half of common tag from the outcome of experiment.