Abstract: To evaluate and compare the actual performance index of atomic magnetometer,four common methods for calibrating the sensitivity indices of atomic magnetometer are described:root mean square,power spectral density,intrinsic sensitivity based on line width and signal-to-noise ratio,shot noise limit.According to the above four methods,the measured data of the nonlinear magneto-optic rotating Rubidium magnetometer are compared and analyzed.The results show that the power spectral density is the most suitable calibration method for the sensitivity of atomic magnetometer,and can reflect the actual performance index of atomic magnetometer.