A new method was presented which was based on finite element method to predict the fatigue life of tower crane's steel structure. With the method, the finite element model of tower crane was developed and the static stress was calculated. And then time history was defined. It was found that there were two main types of fatigue loads acting on tower crane, which were the amplitude load and the impact load. For the amplitude load, a method with field observation and statistical method was proposed and it was found that the frequency of the trolleyjib slipping the stride on the orbit and the beam's coordinate showed statistically normal distributions. And time history of amplitude load was calculated with one day as a cycle. For impact load, taking transient response method, the relationship between internal stress and time was established for main working conditions and the time history was obtained. Taking the static stress of tower crane, time course of amplitude load and time history of impact load as inputs, the fatigue life of steel structure was obtained with the software of MSC.FATIGUE. 