A swing variable voltage technique (CK-Vdd) is proposed to reduce power consume for generic digital circuit system. The proposed CK-Vdd generates a swing variable voltage, which is different from the conventional constant voltage (Vdd) to the digital circuit. The swing voltage is produced from using Voltage Frequency Adjustor (VFA) and Frequency Duty-Cycle Adjustor (FDCA) circuits. The clock rising and falling signals fanin FDCA to generate an adjustable high-low signal to control VFA generates high-low cycling swing voltage. When the clock is at positive-level, a generic positive-edge digital circuit will need large operation current. CK-Vdd supply high-voltage to the digital circuit at this time. On the other hand, when the clock signal transfers to the low-level, CK-Vdd can supply low-voltage to reduce power consumption. From reducing the supply current to the digital circuit at low-level clock, the digital circuit power consumption can be reduced. We implement the CK-Vdd technique in a H.264 video decoder test chip based on TSMC 90 nm CMOS process. The result shows that when CK-Vdd voltage is 0.7v ∼ 0.9v it can save average 32% power consumption. To the maximum, decoder chip can save as high as 45% power consumption.