Abstract: In order to obtain the ductile-brittle transition temperature of 34CrNiMo6 steel used for wind turbine spindle, V-type impact samples were taken at different radial positions, they were tested between -110 ℃ and 25 ℃,the result data was fitted by Boltzman function,then the temperature at 50% of the brittle fracture (FATT50) was obtained from the ductile-brittle transition temperature curve.The brittle and ductile fracture morphology of samples was observed by SEM, the brittle and plastic fracture behaviors of 34CrNiMo6 alloy were briefly analyzed.The results indicated that the ductile-brittle transition temperature of 34CrNiMo6 alloy was between -50 ℃ and -70 ℃, and the transition temperature of spindle surface was lower than that at its core position.Plastic fracture samples showed a typical dimple-like morphology, the fracture surface morphology gradually transited to cleavage fracture as the test temperature decreased.