This article is in the background of lunar exploration program, which requires unmanned operation in the environment of ultra high vacuum, extreme temperature, strong radiation and lunar dust. Seal reliability of lunar sample return devices should be guaranteed as well. Principal prototype devices of explosive welding seal and brazing seal are analyzed separately when applied to lunar program, both of their advantages and disadvantages are indicated, and improved schemes are given as well. Besides, a redundant seal combined with o type rubber ring and knife edge indium alloy is put forward, to validate its reliability, a mathematical model based on Roth theory has been developed to describe sealing mechanism and predict the variable leakage, and the ground tests on leak detection for rubber seal and knife edge seal have been set up separately through helium mass spectrometer. According to the test results, nitrile rubber is proved to be better because of its resilience in alternative temperature, lower leakage and permeation. The knife edge indium seal has lower leak rate, and the welding joint quality of indium alloy itself can be guaranteed as well. The redundant seal is considered to have preliminary feasibility while the test environment for leak detection is required to simulate lunar surface still further.

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