Abstract: The two-channel method is a high-precision, low-lower-limit-of-detection method for measuring the outgassing rate of materials and is suitable for low-outgassing rate materials such as boron carbide. The method needs to determine the background outgassing volume of the measurement system, i.e., after the system pressure is stabilized, the pressure value at a certain moment is selected and calculated as the background outgassing volume. For the device background outgassing measurement, this paper is based on the adsorption diffusion theory, the establishment of a dual-channel measurement system adsorption-diffusion-dissociation model, and numerical calculation and analysis, the study of the system background pressure with the change rule of the temperature, the calculation results are in good agreement with the experimental results. At the same time, this paper carried out the outgassing test on the system containing B4C samples and subtracted the background outgassing of the device to obtain boron carbide values of outgassing rates at room temperature and 150℃. The uncertainty of the outgassing rate measurement of boron carbide was calculated to be 11.78%, which provided theoretical support for the subsequent test research.