The semiconductor bridge (SCB) ignites through bridge film discharge, offering advantages such as low ignition energy, high safety, and compatibility with digital logic circuits. The study uses laser interferometry to investigate the gas dynamics of the bridge film after SCB plasma extinction. Interferometric images of the SCB film gas were obtained through a laser interferometry optical path. After the degradation model of digital image processing, clearer images were produced to facilitate analysis and calculation. The results show that the gas temperature at the center of the SCB film reaches a maximum of 1 000 K, and the temperature rapidly decreases along the axial direction of the bridge surface to room temperature at 300 K. The maximum diffusion velocity of the plasma is 1.8 km/s. These findings provide critical insights for SCB design and ignition control.