Abstract: On-line calibration for multi-parameter, is to fully restore the original state of the instruments, based on which the multi-parameter can be extracted and calibrated with matched standard devices, such as force value, torque, speed, displacement, etc. First, the difference between online calibration and laboratory calibration was briefly introduced, and the implementation process of on-line calibration was exemplified through the specific case. Then the problems and practical difficulties during on-line calibration were described. Finally, the future development of on-line calibration was prospected.