In the outer rain band of Typhoon Haitang, an EF1 tornado struck the Huaian District of Huaian, Jiangsu Province from 18:10 to 18:30 on 1 August 2017. Using the data of conventional observation, NCEP 1°×1° reanalysis data, and Doppler weather radar observation, this paper analyzes a tornado process. The results show that the tornado occurred in the southeast warm and wet jet between the residual low pressure of the typhoon and the edge of the subtropical high. One hour before the occurrence, the smallscale vortex appeared on the ground and moved along the ground convergence line. The adjacent ground automatic station observed an increase in air pressure, a decrease in temperature and dew point, and a significant increase in wind force when the tornado passed by. Increasing convective available potential energy, small convection inhibition energy, large vertical wind shear between 0 and 1 km, low lifting condensation level, and dry intrusion were all conducive to the formation of this tornado storm. Huaian Doppler radar detected the inflow gap, TVS characteristic, and cyclonic wind field structure. Based on the vertical helicity analysis and double Doppler radar wind field inversion methods, the structures and evolutions of tornado are studied. It is found that the smallscale vortices had generated in the vertical wind shear of the lower environment before the tornado occurred. The horizontal wind field was dominated by convergence. When the tornado occurred, the descending of cyclonic convergence center was favorable for the vortex to touch the ground. The tornado appeared on the left front of the vortex in the lower level and formed in the horizontal wind shear below 1.5 km.