With the increasing usage of non-linear devices, harmonic problem has become more and more serious in power grid. The shunt capacitor is very susceptible to harmonics because of its capacitive resistance. But existing capacitor protectors don’t take into account the influence of harmonics, resulting that shunt capacitor cannot be effectively protected under the harmonic surroundings. This paper analyzes the harm of harmonics to capacitors, puts forward new harmonic protection methods and setting rules, and designs a microprocessor-based harmonic protection equipment based on OMAP-L138 processor which can realize single harmonic protection and total harmonic distortion rate protection besides common protections for shunt capacitor. Finally, the accuracy and error of the harmonic protection equipment is verified by laboratory test. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 5211SX16000H).