To explore the failure mode of high voltage transmission steel tube tower key nodes under multi-scale model in extreme climatic conditions, the research, taking a large crossing tower as the research background, proposes a method to achieve connection of different scale units with the finite element software ABAQUS,and verify the rationality of the multi-scale connection. Build the multi-scale transmission steel tube tower model of structure behavior agreement, and prove the rationality of the multi-scale model through the contrast analysis. Make numerical simulations on three kinds of extreme climates conditions: wind, ice covered and wire wire broken fracture, and obtain the failure modes of transmission tower key nodes under different working conditions based on the analysis of simulated results. The research would provide a reliable basis for the design, maintenance and reinforcement of high voltage transmission steel tube towers.