Abstract:[Purposes] In order to enrich the evaluation index system about the academic influence of journals, we propose a novel method which named f(x)-index.[Methods] Taking the 34 LIS journals of the china S&T journal citation reports of 2012 as examples, we acquired the published article volume and cited frequency of each journals through CNKI and calculated the corresponding parameter values by excel and C++ tools, in the end, ranking those journals according to the f(x)-index.[Findings] Compared with the CSSCI core periodical, the accuracy of evaluation results is about 94.12%. With analysis of correlation of each index, we find that the f(x)-index has a strong positive correlation with a variety of journals evaluation index which includes impact factor.[Conclusions] The f(x)-index not only considers the numbers of publications, citation count and average of citation count, but also the differences between low cited and high cited papers by using the properties of logarithmic function, which can be used as the evaluation of academic influence about journals.