A tip-grounded waveguide microsensor was proposed to overcome the difficulty of quantitative voltage calibration in electrooptical detection for integrated circuit (IC) test. On this basis, we optimized the thickness of the electrooptical material of the sensor to eliminate the influence of the circuit layout on the measured signals. The improved sensor in return made it possible to calibrate the voltage with known reference electric signals quantitatively. This method circumvented the uncertainty of the probe conditions of each measurement point. Finally, a calibration accuracy of better than 6% was obtained, which satisfied broad applications in the IC industry.