The invention provides a trace gas detection method based on a micro resonance loop array spectrum-dividing technology and a detector. In the method, infrared laser firstly passes through a gas chamber, and then enters a micro resonance loop array consisting of a plurality of circular or racetrack micro resonance loops for coupling and spectrum-dividing; resonant wavelength light in the infrared laser after passing through the gas chamber is coupled and output by download waveguides of corresponding micro resonance loops; the light intensity of the coupled and output light is detected by photodetectors; and the components and the concentration of a gas to be tested are detected according to the change of the light intensity. The detector has a structure that a light source is connected with the gas chamber through a light path or optical fiber, the light output end of the gas chamber is connected with upload waveguides through an optical fiber and waveguide coupling device, the plurality of photodetectors are respectively connected with the plurality of download waveguides, and the micro resonance loop array is arranged between the upload waveguides and the download waveguides. The invention has skilled design, can be used for simultaneously detecting a plurality of gases with high detection accuracy, and can realize the integration and the portability of the detector.