The present invention relates to a flexible low-voltage transformation ratio measurement instrument used in the field of electric measurement. A host comprises a voltage measurement circuit, a currentmeasurement circuit, a display, a host processor and a Bluetooth module. The instrument performs a whole measurement process to achieve measurement of the frequencies and amplitudes of a low voltageand a low-voltage current, electrical parameters such as the transformation ratio polarity and the low voltage of the low-voltage current and the power and the power of each low-voltage current, a measurement result is displayed through the display, or the measurement result is sent to an intelligent terminal through the Bluetooth module, and the intelligent terminal reads the data. The large-current signals of the measurement instrument are measured through a flexible coil current clamp with a large caliber to perform convenient measurement of the low-voltage large current in the field application.