The elevator landing door is one of the special equipment components that have the closest contact with the public. It is an important physical barrier that separates the floors from the hoistway. In the event of a fire in a high-rise building, complete lift landing doors play an important role in preventing the spread of toxic fumes across floors. It is not an easy task to test and determine the smoke blocking ability of lift landing doors under fire conditions. Generally, the combustion test furnace and the collection and measurement of specific gas (CO 2 ) are used to estimate the amount of smoke gas leakage. In this paper, a burner and gas (CO 2 ) collection system for lift landing doors were built, the calculation formula of flue gas leakage suited for the integrity of lift landing doors was deduced, the differences in the results of processing smoke gas leakage with multiple mathematical method steps was described. Then, the test results of smoke leakage from lift landing doors without fire-resistant design and with three fire-resistant measures were analyzed. Finally, some design suggestions for improving the fire-resistance integrity of lift landing doors were put forward.