In the calibration methods for high energy laser(HEL) energy measuring equipment, the online calibration method can eliminate vourous effect imposed on measurement results by extrinsic elements. Three online calibration methods were introduced to analyse the theories and data treatment processes. Since several parameters are unknown, least square fitting method was used. The ratio of reflectivity to the spectroscope transmittance was calibrated online to eliminate its uncertainty imposed on the measurement results. By analyzing and comparing data of the three methods conclusions show that direct transfer method is the simplest which can eliminate effect caused by environment elements, laser beam spot characteristic, and so on. Indirect transfer method can eliminate the effect caused by almost all extrinsic elements including change of the ratio of reflectivity to transmittance, but its calibration processes are complex, its uncertainty in measurements is the biggest. Calibration processes of intersectional transfer method are simpler than indirect transfer method’s. It can also eliminate effect caused by changes of the ratio of reflectivity to the spectroscope transmittance, and its data treatment processes are the simplest.