A non-contact voltage sensor comprises: a sensing electrode, the sensing electrode is provided with a space for a measured conductor to pass through, an input coupling capacitor is formed between the measured conductor and the sensing electrode, and grounding impedance is formed between the sensing electrode and the ground; at least one feedback conductor which penetrates through the sensing electrode, wherein a feedback coupling capacitor is formed between the feedback conductor and the sensing electrode, and the feedback coupling capacitor is proportional to the input coupling capacitor; a signal amplification module, wherein the output end of the sensing electrode is connected with the input end of the signal amplification module, the output end of the signal amplification module is connected with the feedback conductor, the signal amplification module outputs a voltage measurement result, and the signal amplification module is used for amplifying an alternating current voltage signal sensed by the sensing electrode and performing phase shift on the voltage signal, the amplitude of the voltage output by the signal amplification module and the amplitude of the to-be-measured voltage form a linear relation, and the phase of the voltage is opposite to the phase of the to-be-measured voltage. According to the invention, a closed-loop sensing principle is adopted, and non-contact measurement of amplitude, phase and frequency of alternating voltage can be realized.