Abstract: The atomic cluster production in TOF MS experiments was believed to be a statistical process, and it should act in accordance with the probability laws. By analysis the structure of C_n,S_n,Al_n and B_n cluster mass spectrum in our experiments, it is found that the size-distribution of those clusters with same structure is controlled by lognormal statistics, and the distribution is changed with the structure variation. This approach can be used to determine where the cluster’s structure is begined to changed, and is thus developed to a general method for interpreting mass spectra.