Self-Similar & Stochastic Evolution Mechanism of Large Software File Name Length

File name length evolution mechanism of large software is researched in the present paper. Our statistical fact: large software file name length follows lognormal distribution, brings us the conjecture on file name growing process with self-similar and stochastic growth dynamics implied by Gibrat´s law. Based on our empirical results, a model is proposed to simulate the growth of large software file name length with self-similar and stochastic evolution mechanism. Both the numerical simulation and theory analytical results, finally, show that the proposed model makes a good agreement with the empirical data, and hence the conjecture is proved to be correct and our model can simulate the underlying evolution law of large software file name growth.