In order to research a new detection principle of capacitive sensor, a new capacitive sensor based on the edge effects of non-parallel polar plates is proposed in this paper. The capacitance field of the sensor includes two parts, the electric field between the polar plates and the edge electric field. When a special medium is in the edge electric field, it will change the distribution of the electric field line of the edge electric field and cause the change of the capacitance value of the sensor, and then the non-contact detection of the detected object can be realized. This paper studies the relationship between the range of the edge electric field and the basic parameters of the sensor. The model and formula of the sensor are analyzed theoretically in this paper, and these typical projects were simulated by ANSYS. The results show that the detection principle of the new capacitive sensor is reasonable and correct.