Abstract: In order to reach the anti-fatigue design of high-soft tower of low wind speed wind turbine,taking a 140 m soft tower as the research object,the vortex induced vibration fatigue damage assessment uses the effective correlation length method and spectrum model method recommended by EU standard EN1991-1-4. Acquire inherent modal attributes of the structure by modeling based on finite element method;Derive the fatigue stress range and damage rule of tower from S-N curve,Rayleigh distribution of wind speed and Miner rule;The critical wind speed distribution and weld fatigue damage distribution of soft tower and rigid tower are compared and analyzed. The results show that the soft tower is easier to excite the second-order vortex induced vibration,the second-order vortex induced load increases significantly,and its damage is extremely sensitive to different wind field conditions（annual average wind speed and wind shear）;Under the design wind speed of 6.5 m/s,the fatigue damage at 45%-85% of the tower height exceeds the 20-year damage limit of IEC 61400-6 requirement for tower and foundation design by 0.1. There is a risk of fatigue damage,so it is necessary to consider the resistance adding measures or optimize the structural design.