The influence of different vermicularizing rates (55%, 70%, 90%) on thermal fatigue behavior of vermicular graphite cast iron was studied by heating and cooling and V-notched sample. The results show that the thermal fatigue resistance of vermicular graphite cast iron increases first and then decreases with the increase of vermicular graphite. When the vermicularizing rate is 70%, the thermal fatigue resistance of vermicular graphite cast iron is the best. The mechanism of crack initiation and propagation of vermicular graphite cast iron is significantly different with different vermicularizing rates. When the vermicularizing rate is 90%, the V-notched crack is obviously initiated, and the main crack generated a secondary crack along the vermicular graphite. Finally, the V-notched form a collapse trend. However, when the creep rate is 70% and 55%, the cracks near the V-notched are significantly reduced, and only a small number of tiny cracks are generated in the tip of the spheroidal graphite and the matrix, and the cracks do not expand significantly, with a low tendency to generate cracks, and the V-notched depression does not form collapse.