The invention discloses a generation-transformer group overexcitation protection method based on a half-wave integral algorithm. The generation-transformer group overexcitation protection method basedon a half-wave integral algorithm uses a half-wave integral accumulation algorithm to directly connect the secondary side voltage of a voltage transformer to a CPU, and then calculates the overexcitation multiple. The generation-transformer group overexcitation protection method based on a half-wave integral algorithm no longer uses a complicated and cumbersome analog circuit susceptible interference, and can completely avoid the problems caused by the pre-engineering analog circuit. The half-wave integral accumulation method implemented by software is realized by a computer program, thus being convenient and flexible, and being easy to modify in the field. The generation-transformer group overexcitation protection method based on a half-wave integral algorithm improves the sensitivity ofoverexcitation protection to voltage frequency variation, ensures the accuracy and stability of the overexcitation multiple calculation when the frequency variation in the protection measurement frequency range is large, and improves the reliability of the overexcitation protection.