An improved absolute calibration technology based on indirect measurements was developed through two probative experiments, the performance of which was evaluated by applying the approach to in situ sea surface height(SSH) at the Tianheng Island(tidal gauge) and the satellite nadir(GPS buoy). Using Geoid/MSS(mean sea surface) data, which accounted for a constant offset between nadir and onshore tidal gauge water levels, and TMD(tidal model driver), which canceled out the time-varying offsets, nadir SSH(sea surface height) could be indirectly acquired at an onshore tidal gauge instead of from direct offshore observation. The approach extrapolated the onshore SSH out to the offshore nadir with an accuracy of(1.88±0.20) cm and a standard deviation of 3.3 cm, which suggested that the approach presented was feasible in absolute altimeter calibration/validation(Cal/Val), and the approach enormously facilitated the obtaining SSH from the offshore nadir. An improved absolute calibration technology based on indirect measurements was developed through two probative experiments, the performance of which was evaluated by applying the approach to in situ sea surface height (SSH) at the Tianheng Island (tidal gauge) and the satellite nadir (GPS buoy Using Geoid / MSS (mean sea surface) data, which accounted for a constant offset between nadir and onshore tidal gauge water levels, and TMD (tidal model driver), which canceled out the time-varying offsets, nadir SSH The approach extrapolated the onshore SSH out to the offshore nadir with an accuracy of (1.88 ± 0.20) cm and a standard deviation of 3.3 cm, which suggested that the approach presented in feasible in absolute altimeter calibration / validation (Cal / Val), and the approach enormously facilitated the obtaining SSH from the offshore nadir.