There are some problems in the traditional transient temperature test equipment. The thermal inertia is great, and can only be a single point of detection. To be able to achieve real-time monitoring for transient temperature distribution change of the gun body surface, the test system for transient temperature distribution was designed based on Speckle Pattern Interferometry (SPI) and spectroscopy. In the system, transient temperature change of the barrel led to slight deformation, and it was converted into speckle interference fringes by SPI technology. Spectral distribution function was obtained by the interference fringes by the Fourier transform, so the information of interference fringe deformation was incorporated into the frequency domain. The data of temperature distribution can be inverted on any sampling time by spectral distribution function. In experiments, the ZX-FB1 fiber optic thermometer was used to test transient temperature on a single point as the standard value. The center wavelength of the laser was 555 nm, and the speckle pattern interference fringes were collected by area array CCD. Image Recognition-Speckle Pattern Interferometry (IR-SPI) and Fourier Transform-Speckle Pattern Interferometry (FT-SPI) were used in experiments, the calculation of transient temperature was completed through two methods. Experimental results are that both methods can achieve transient temperature detection. But the FT-SPI is higher in terms of accuracy, and it can effectively overcome the gross error caused by the surface defects, paint wear and other similar problems.