Abstract: EH40 high-strength steel is one of the important basic materials for the construction of polar ships in the future.In order to study the fatigue properties of EH40 high-strength steel and its welded joints in low temperature environment, the submerged arc welding(SAW) of TMCP produced EH40 high-strength low-temperature steel plate was carried out, and the microstructure and mechanical properties of the welded joints were analyzed. The low temperature fatigue properties of the base metal and welded joint were tested by fatigue testing machine. The results show that the microstructure of EH40 steel produced by TMCP process is dominated by proeutectoid ferrite(PF)+ granular bainite, while the microstructure of CGHAZ is dominated by bainite and that of FGHAZ is dominated by PF. Compared with the tensile results at room temperature, the strength of base metal and welded joint at 0 ℃ and-20 ℃ increases. With the decrease of temperature, the fatigue S-N curve of base metal and welded joint also moves upward, indicating that the fatigue performance of the material at low temperature is better than that at normal temperature. The fatigue fracture analysis shows that the fatigue crack source mainly originates from the surface. The dislocation density inside the metal material increases with the increase of cycle times. Fatigue load causes the generation of dislocation inside the material, and the dislocation plugging is easy to form at the grain boundary,which becomes a potential crack source.