The invention belongs to the technical field of trace gas detection, and relates to a multi-cavity type half-open resonance photoacoustic cell and a system for measuring gases simultaneously. The photoacoustic cell comprises a plurality of resonant cavities, wherein the lengths of the resonant cavities are different, so that the resonant frequencies of the resonant cavities are different, and therefore each resonant cavity corresponds to a gas to be measured. An acoustic sensor sensitive diaphragm is fixed on the end face of one side of the photoacoustic cell, and photoacoustic signals of different frequencies generated in the plurality of resonant cavities act on the acoustic sensor sensitive diaphragm, so that periodic vibration of the acoustic sensor sensitive diaphragm is caused, and the concentration information of various gases to be measured can be obtained by demodulating and analyzing the vibration condition of the acoustic sensor sensitive diaphragm. The structural design ofthe photoacoustic cell is more simplified, the middle position of the resonant cavity does not need to be perforated to be matched with an acoustic sensor for use, and the processing difficulty of thephotoacoustic cell is reduced. Meanwhile, the volume of one buffer chamber is reduced through the design, so that the gas balance time is shortened, and a new solution is provided for simultaneous measurement of high-sensitivity gases.