Abstract: This study is based on the compositional fluctuation characteristics in the mass production of 17CrNiMo6 gear steel forgings. Through Deform-3D multi physics coupling simulation, the influence mechanism of alloy compositional fluctuation on carburizing rate and hardness distribution is revealed. Research has shown that the sensitivity of carbon diffusion coefficient to compositional fluctuations is significantly higher than that of transfer coefficient, and compositional differences only have a significant impact in the early stages of heating and carburizing; The carbon flux during the initial stage of carburization shows a negative correlation with the initial carbon content, and the carburization rate of the lower limit sample is higher than that of the upper limit sample; The carbon concentration gradient in the root region is higher than that in the tooth profile, but its spatial differences are not significantly correlated with component fluctuations; The consistency of surface hardness is dominated by the carburizing process, while the difference in core hardness is directly controlled by compositional fluctuations; The gradient of tooth root hardness is higher than that of tooth profile, but its formation mechanism is independent of component fluctuations.