Abstract: A D-dot monitor was designed to measure the voltage of Yang accelerator water transmission line. A signal proportional to the time derivative of the voltage was given with capacitor from high voltage electrode to the probe and the voltage was given with the RC integrator. The parameters (inductance and capacitance) were estimated using the transient analysis of OrCAD/Pspice and the amplitude-frequency response of the monitor was analyzed. The result of measurement can be explained using the analysis. The monitor was calibrated in-situ with resistive divider while accelerator was short-circuit at lower Marx-bank charge voltages. The experimental result indicates that the designed D-dot monitor is satisfactory to the measurement requirement.