The invention relates to the field of detection of a lithium battery, and particularly relates to a gas collection method used for analysis of gas production inside the lithium battery. An inner core of the to-be-analyzed lithium battery is subjected to a gas production test after being primarily packaged by an elastic sealing material, the analysis stage is chosen, the elastic sealing material is secondarily packaged after being clamped along the periphery of the inner core of the lithium battery, and then the produced gas is stored and packaged into a gas pocket. According to the technical scheme, the gas produced by the soft packaged lithium battery is conveniently collected, the foreign gas is avoided, and the in-situ analysis of a component is facilitated. The gas pocket is substantially in-site collection of the gas, meanwhile, the free position transfer of the gas pocket is implemented, so as to be favorable for the test on an analytical instrument like a gas chromatograph, as well as the in-site analysis of the produced gas composition and the mechanism of the lithium battery.