Highly versatile machines,such as wheel loaders,forklifts,and mining haulers,are subject to many kinds of working conditions,as well as indefinite factors that lead to the complexity of the load.The load probability distribution function (PDF) of transmission gears has many distributions centers; thus,its PDF cannot be well represented by just a single-peak function.For the purpose of representing the distribution characteristics of the complicated phenomenon accurately,this paper proposes a novel method to establish a mixture model.Based on linear regression models and correlation coefficients,the proposed method can be used to automatically select the best-fitting function in the mixture model.Coefficient of determination,the mean square error,and the maximum deviation are chosen and then used as judging criteria to describe the fitting precision between the theoretical distribution and the corresponding histogram of the available load data.The applicability of this modeling method is illustrated by the field testing data of a wheel loader.Meanwhile,the load spectra based on the mixture model are compiled.The comparison results show that the mixture model is more suitable for the description of the load-distribution characteristics.The proposed research improves the flexibility and intelligence of modeling,reduces the statistical error and enhances the fitting accuracy,and the load spectra complied by this method can better reflect the actual load characteristic of the gear component.