The invention relates to a device for improving tuning stability of a series resonance test under small load. The device comprises a column type voltage regulator, an exciting transformer, a tuning inductor, a measurement voltage divider, a measurement module, an upper computer, and a damping resistor, wherein an output end of the column type voltage regulator is connected to a power supply, and the output end is connected to an input end of the exciting transformer; an output end of the exciting transformer is connected in series with the tuning inductor and a test capacitor to form a closedloop; the measurement voltage divider is connected in parallel with the test capacitor, output ends of the measurement module and the measurement voltage divider are connected with an upper computer,an input end of the measurement module is connected with the exciting transformer, and the damping resistor is connected in series between the exciting transformer and the tuning inductor. Compared with the prior art, the device connects the damping resistor in series between the output end of the exciting transformer and the tuning inductor, so that tuning of the series resonance test under smallload is more stable, and the tuning speed is higher.