The invention discloses a voltage sensor based on an alloy resistor and an implementing method thereof. The gap of electrical connection between the primary part and the secondary part of power equipment is broken, and the complicated physical process of electromagnetic conversion or optical conversion is not needed to transfer voltage measuring information between the primary equipment and the secondary equipment. By adopting the high-precision alloy resistor and a large-resistance device, the voltage of the large current, flowing through the alloy resistor, of a to-be-measured branch is within the input range of weak electric measuring equipment. By measuring the voltage, and combining the known alloy resistance value, the current value of the measured branch can be simply and conveniently measured. According to the known resistance value of the large-resistance device and the resistance value and current value of the alloy resistor, the voltage of a measuring point can be measured. Compared with the traditional voltage transformer, the voltage sensor has the advantages that the temperature drift is avoided, the mechanical vibration-resistant performance is realized, the frequency characteristic is good, the alternating current and the direct current are universal, the size is small, the assembly is realized, and the like.