This paper proposed a method to accomplish scan test low-power optimization through voltage control. This method is named voltage-control method for short. It controls the power supply of combination logical units mainly through gating transistor insertion. It effectively solves the problem of the useless propagation to combination logic from test signals in the process of the shift-in of scan test. The power supply of combination logic is controlled, thus the voltage-control method not only effectively reduces useless dynamic power, but also substantially reduces the leakage current static power caused by power supply. Also the insertion of gating transistor has little influence on the designed area and timing sequence. The experiment result has shown that the voltage-control method has much less influence on the area and delay than the logic gate insertion method, and also, the power optimization is improved by nearly 32%.