The invention discloses a device and method for improving performance of a photoacoustic spectral trace gas sensor. The device comprises a pulsed laser, a laser collimation system, a thin film polarizer, a first right angle prism, a Pockels cell, a photoacoustic cell, a second right angle prism, a preamplifier, a control and data acquisition system, and a computer, wherein the pulsed laser, the laser collimation system, the thin film polarizer, the first right angle prism, the Pockels cell, the photoacoustic cell and the second right angle prism are sequentially set in the beam propagation direction; a microphone is disposed in the photoacoustic cell and connected to the preamplifier; the preamplifier is connected to the control and data acquisition system; and the control and data acquisition system is connected to the computer. The device and method provided by the invention utilize a Pockels cell to change the polarization state of the laser and two right angle prisms to achieve multiple reflections of the beam.