The invention discloses a self-calibration method of a calibration instrument, which comprises the following steps that: (1) a control unit and a self-calibration unit are arranged on the calibration instrument with a measuring unit and an output unit, wherein the control unit is connected with the self-calibration unit, the self-calibration unit comprises a selector switch unit, and the selectorswitch unit is respectively connected with the measuring unit and the output unit; (2) time intervals for carrying out self-calibration by the calibration instrument are set on the control unit; (3) after the calibration instrument is started up or the time intervals for self-calibration are reached, the control unit controls the self-calibration unit to automatically measure self-calibration; and (4) by adopting measurement subjected to self-calibration as a reference, the control unit controls the self-calibration unit to automatically output self-calibration. Compared with the prior art, the self-calibration method of the calibration instrument solves the technical problems that the calibration instrument carries out self-calibration through manual operation and the precision of the calibration instrument can be affected by time and environment changes.