Using the ECMWF Interim ReAnalysis (ERAInterim) data from 1989 to 2008 and the simulations from 1980 to 2019, which are produced by a chemistry-climate model, variation characteristics and trends of the tropical tropopause layer (TTL) structure are analyzed. It is found that the TTL characteristics have significant seasonal and spatial variations. The thickness of the TTL in summer and autumn is the thinnest in the Northern Hemisphere and it has the largest seasonal variability in winter in the Northern Hemisphere. ERA-Interim data indicates that the TTL temperature increased significantly in 1991 because of the Pinatubo volcanic eruption, and the temperature decreased after that from 1992 to 1995. The TTL temperature has been increasing since 1996 without considering the impact of Pinatubo volcanic eruption. In recent years the TTL is getting higher, warmer and thinner， and the stratospheric water vapor is also increasing. The chemistry〖CD*2〗climate model simulations show the same trends.