In this paper , we try to improve the magnetogram calibration method of the Solar Magnetic Field Telescope ( SMFT ) .
The improved calibration process fits the observed full Stokes information , using six points on the profile of Fe ı 5324.18 Ã line , and the analytical Stokes profiles under the Milne-Eddington atmosphere model , adopting the Levenberg-Marquardt least-square fitting algorithm .
In Comparison with the linear calibration methods , which employs one point , there is large difference in the strength of longitudinal field B _ { l } and tranverse field B _ { t } , caused by the non-linear relationship , but the discrepancy is little in the case of inclination and azimuth .
We conclude that it is better to deal with the non-linear effects in the calibration of B _ { l } and B _ { t } using six points .
Moreover , in comparison with SDO/HMI , SMFT has larger stray light and acquires less magnetic field strength .
For vector magnetic fields in two sunspot regions , the magnetic field strength , inclination and azimuth angles between SMFT and HMI are roughly in agrement , with the linear fitted slope of 0.73/0.7 , 0.95/1.04 and 0.99/1.1 .
In the case of pores and quiet regions ( B _ { l } < 600 G ) , the fitted slopes of the longitudinal magnetic field strength are 0.78 and 0.87 respectively .