This paper proposes an electronic-tuning frequency stabilization scheme with power tuning for a Watt-level terahertz gyrotron oscillator in gyro-BWO state. The intrinsic positive relationship between electron-beam pitch factor a and accelerating voltage V in electron gun contributes to Doppler shift compensation during electronic tuning. When the pitch factor a varies from 1.1 to 1.9, the prototype three-sectioned gyrotron oscillator can be fixed at 253.98 GHz with 10 MHz level error. The output power is tuned by 40% from maximum. This approach is of importance for heat-effect-oriented applications in biomedicines and material processing.