The electric field has a very significant effect on the working conditions of electrical equipment. A passive electric field sensing system is developed to measure electric field strength based on the electric field induction theory. This paper studies an electric field sensing system comprising a probe head radius of 30 mm and a potential electrode radius of 18 mm. The testing system of the power frequency electric field is established according to GB/T12720-1991, and the calibration test experiment of the sensor is carried out. With a capacitance of 350 pF and a frequency electric intensity value of <;12 kV · m-1, the sensor system has good linearity with a nonlinearity error of ~6.68%. The results of the study indicate that the sensory system meets the requirements of practical engineering.