The invention discloses an anti-interference high-precision zero-crossing detection method, which is characterized in that a programmable logic device FPGA (Field Programmable Gate Array)/CPLD (Complex Programmable Logic Device) starts counting when detecting a falling edge of a square wave signal S3 outputted by a first optocoupler switch circuit, and outputs a narrow-pulse signal through an I/O when counting to half of a previous cyclic wave counting number of an alternating current signal, wherein the narrow-pulse signal is marked as S5, namely a zero-crossing point of the alternating current signal at the current cyclic wave; and the programmable logic device FPGA/CPLD stops counting when detecting a falling edge of a square wave signal S4 outputted by a second optocoupler switch circuit, wherein the counting number serves as a counting number of the alternating current signal at the current cyclic wave. The method disclosed by the invention is not sensitive to amplitude fluctuations of the detected alternating current signal, can lock a zero-crossing point of the fundamental wave alternating current signal at a midpoint moment between the falling edge of the square wave signal S3 and the falling edge of the square wave signal S4, and then the zero-crossing point of the fundamental wave alternating current signal can be judged accurately in the programmable logic device FPGA/CPLD through simple program processing. The method has the advantages of high interference resistance, high applicability and high precision.