The invention relates to a three-band WiFi antenna, comprising a radiator, a dielectric substrate, a metal ground, a feeder line and a parasitic resonance groove. The radiator is composed of three rectangular metal patches with different sizes, the feeder is L-shaped metal patch, and the parasitic resonance groove is a groove having the shape of the Chinese character 'hui' and excavated in the metal floor; the radiator is composed of three rectangular metal patches with different sizes, which are divided into an upper rectangular metal patch, a middle rectangular metal patch and a lower rectangular metal patch. Each rectangular metal patch is arranged in parallel along the direction of its long side. The middle rectangular metal patch has the largest size, and its left narrow side is connected with the microstrip feeder as the main radiating part of the antenna. The upper rectangular metal patch and the lower rectangular metal patch are close to the middle rectangular metal patch, andplay the role of enhancing the coupling between the radiator and the parasitic resonance groove.