Abstract:Based on NCEP reanalysis data, conventional observations data, surface dense observation data and Doppler radar data, the environmental background of 10 tornadoes which occurred within spiral rain belt of typhoon and the evolution characteristics of echo structure of the tornadoes in F2 class and above were studied in detail. The results show that, firsthy typhoon tornadoes occur in an environment with the weak convective available potential energy (200-1000 J·kg-1) and strong low level vertical wind shear where the vertical wind shear between 0 and 1 km more than 10-2s-1. The storm relative helicity is very great and the typhoon tornado environment average bulk Richardson number is small, averagely below 40. Typhoon tornadoes mostly occur on the right sides of the moving paths of the typhoons where the 0-1 km vertical wind shear and storm relative helicity are greater.Typhoon tornadoes are mainly generated in the spiral rainbands in the outside region of the typhoons. Before tornadoes come into being the convergence of wind direction and speed appears near the surface, but the temperature gradient is small. Secondly, the storms which produce typhoon tornadoes are mini supercell storms, with cell centroid being about 2 km and stretching height about 5-7 km, accompanying the mesocyclones in horizontal scales about 2-4 km. The positive vertical vorticity is limited to below 4 km.