A nondestructive method for measuring the electrical conductivity of doped GaAs wafers using a compact microwave instrument is presented. Based on the characteristics of the microwave detector and the fact that the microwave measurement is independent of the thickness of the wafer, the analytical and explicit expressions to evaluate the electrical conductivity of the wafer are derived. Using this method, only the voltages of the reflected signals for two wafer samples whose conductivities are known are required to calibrate the two undetermined constants in the equation. Then, the conductivity of any other wafer can be evaluated by substituting the measured voltage of the reflected signal into the explicit expressions. Seven different doped GaAs wafers with thickness larger than 350 μm and conductivities in the range of 1.3 × 104 S/m to 7.6 × 104 S/m are measured in the experiment, two of which are used for calibration. The evaluated results agree well with those obtained by the conventional Hall effect measurement method, with an evaluation error less than ±4.5%. The proposed method is potentially useful for the contactless and nondestructive evaluation of the electrical conductivity of any kind of semiconductor wafer.