The invention relates to an intelligent substation 3/2 wiring bus reactive power calibrator based on conventional instrument transformers. According to the calibrator, an interval measuring device (4) is connected with secondary loops of a conventional current transformer (3) and a conventional voltage transformer (1) via a merging unit (2) so that the current from the secondary side of the conventional current transformer (3) of the branch circuit flowing to the merging unit (2) and the voltage form the secondary side of the conventional voltage transformer (1) connected to the merging unit (2) are obtained, and data is transmitted to a measuring main desk (5) via a WLAN interface; and finally, the data transmitted via the WLAN interface and data obtained from an MMS network of a substation are compared via a main desk display panel (9). According to the calibrator, only 1 or 2 people are needed for operation, more importantly, the measuring condition of the reactive power of a bus measuring and control device arranged in a protection small cell can be conveniently and rapidly checked and verified, the measuring synchronization performance of each branch of a bus can be guaranteed, and the calibrator can be applied to the field of calibration of the intelligent substation based on the conventional instrument transformers.