A GIS electronic instrument transformer test system based on opening-closing small capacity current of an isolating switch, comprising: two casings, wherein a GIS pipeline is arranged between the two casings, one casing is a power supply casing, the power supply casing is connected with a high voltage test transformer and a capacitive voltage divider used for protecting a power supply, which are connected in parallel each other, the capacitive voltage divider is used for reducing a resonance effect caused by higher power supply impedance, the other casing is a load casing, the load casing is connected with a load capacitor, and a first isolating switch is arranged in the GIS pipeline close to the power supply casing, is characterized in that: a first calibration primary transient test system, a first to-be-tested electronic instrument transformer, a second to-be-tested electronic voltage transformer and a second calibration primary transient voltage test system are arranged between the first isolating switch and the load casing; wherein, the first to-be-tested electronic instrument transformer is close to the first isolating switch, the second to-be-tested electronic voltage transformer is close to the load casing, the first to-be-tested electronic instrument transformer is an electronic current transformer or an electronic combined current and voltage transformer, the first calibration primary transient test system is arranged near the first to-be-tested electronic instrument transformer and is a primary transient current test system corresponding to the first to-be-tested electronic instrument transformer or a combination of primary transient voltage and current test systems, and the second calibration primary transient voltage test system is arranged near the second to-be-tested electronic voltage transformer; one end of a secondary converter is connected with the to-be-tested electronic instrument transformers, the other end of the secondary converter is connected with a merging unit, the other end of the merging unit is connected with a fault recorder, and the fault recorder is used for connecting the output of the merging unit. a first calibration primary transient test system, a first to-be-tested electronic instrument transformer, a second to-be-tested electronic voltage transformer and a second calibration primary transient voltage test system are arranged between the first isolating switch and the load casing; wherein, the first to-be-tested electronic instrument transformer is close to the first isolating switch, the second to-be-tested electronic voltage transformer is close to the load casing, the first to-be-tested electronic instrument transformer is an electronic current transformer or an electronic combined current and voltage transformer, the first calibration primary transient test system is arranged near the first to-be-tested electronic instrument transformer and is a primary transient current test system corresponding to the first to-be-tested electronic instrument transformer or a combination of primary transient voltage and current test systems, and the second calibration primary transient voltage test system is arranged near the second to-be-tested electronic voltage transformer; one end of a secondary converter is connected with the to-be-tested electronic instrument transformers, the other end of the secondary converter is connected with a merging unit, the other end of the merging unit is connected with a fault recorder, and the fault recorder is used for connecting the output of the merging unit.