Abstract: The fatigue behavior of welded steel structure of tanker under different service conditions was studied. Three typical road conditions, super highway, highway and rugged road were selected. The hot spot stress was calculated by strain measurement at different positions, and the load spectrum was compiled according to the processed data by rain-flow method. Thereafter, the fatigue life of each position was calculated according to the theory of linear cumulative damage. The results showed that the different positions of welded structure had different fatigue life under different service conditions, and the dangerous positions were 9 and 10, which had the lowest fatigue life on the super highway. Combined with the road conditions and driving behavior, the real-time observation of the waveform showed that the emergency brake, climbing slope or getting down slope and turning would have a greater impact on the fatigue life compared to the road roughness.