Abstract: The ultra-large spacecraft remote sensor evaluation system is a test device used for performance testing and evaluation of large-diameter optical remote sensors under the conditions of a simulated in-orbit environment on the ground, consisting of a vacuum vessel, a low-temperature heat sink system, a vacuum acquisition system, a nitrogen flow system, an external heat flow simulation device and so on. The vacuum vessel is the main body of the evaluation system of the very large spacecraft remote sensing device, and its structure is complex; the number of openings is large, the volume is huge, there are many leakage factors, its leakage rate index is the key factor affecting the spacecraft ground simulation test work vacuum degree index can be achieved. This paper presents a comparative analysis of the helium mass spectrometry leak detection methods for each stage of the vacuum vessel development process. Based on the analysis of the difficulties in locating leaks in the development process of very large vacuum vessels, the use of helium mass spectrometry vacuum sampling is proposed to achieve rapid and efficient leak location in the development process, and good results are achieved in practical applications.