The invention discloses a device and a method for tracking the resonant frequency of a photo-acoustic cell. By adopting a multilevel sweep frequency principle, the precise acquisition of the resonant frequency of the photo-acoustic cell can be realized, and the resonant frequency of the photo-acoustic cell can be tracked and obtained by less sound waves with different frequencies within a shorter time; the range and the precision of the resonant frequency tracking can be configured according to the practical condition of photo-acoustic gas detection, and the tracking of the resonant frequency of the photo-acoustic cell can be efficiently finished; and a speaker is installed in a buffering room or a resonant section of the resonant photo-acoustic cell, a rheomicrophone is installed in the resonant section, and the functions of frequency tracking and photo-acoustic signal resonance detection are realized by time-sharing of the photo-acoustic cell. The invention has the advantages of fast and exactly tracking the resonant frequency of the photo-acoustic cell on line, efficiently improving the detection sensitivity of gas, resisting noise jamming of environment, and providing approaches and manners for the practicability of the photo-acoustic gas detection by a resonance method.