The fireresistant performance of the concrete flue slabs used in Yangtze rivercrossing tunnel in Shanghai is studied in terms of tunnel structure design, flue slab fireresistance design, concrete mixing proportion and concrete fireresistant performance assessment, so as to guarantee the safety of the tunnel in case of fire. The fireresistant performance of the concrete flue slabs is assessed by means of fireresistance test. The test results show that the concrete flue slabs are good in fireresistant performance, which can improve the safety of the tunnel in case of fire.