The invention belongs to the technical field of the detection of trace gas and provides a half-open resonance type photoacoustic cell. The photoacoustic cell comprises a shell, a resonant cavity, a buffer chamber, optical glass window pieces, an acoustic wave sensor, an air inlet and an air outlet. According to the half-open resonance type photoacoustic cell, a buffer chamber on one side of a traditional first-order longitudinal resonance type photoacoustic cell resonant cavity is removed, the acoustic wave sensor is mounted at the place, a buffer chamber on the other side is preserved, and then a half-open photoacoustic cell structure is formed. The acoustic wave sensor is used for collecting sound signals and acquiring concentration information of to-be-tested gas through analytical processing. The optical glass window pieces are mounted on the end surfaces of the buffer chambers and permit excitation light to smoothly pass through, the air inlet is formed in the resonant cavity close to the acoustic wave sensor, and the air outlet is formed in the side wall of the buffer chamber. By utilizing the photoacoustic cell, the photoacoustic signal strength is increased, and the detection limit sensitivity of gas is relatively high; and meanwhile, the processing difficulty of the photoacoustic cell, the balanced time of gas and the volume of gas are reduced, and a new solution scheme is provided for the detection of high-sensitivity trace gas.