Abstract: A low-pass filtering method of Barnes-Shapiro’s type has been improved to obtain a bandpass filtering method, which has the good response to the selected mesoscale wave length. This method has been applied to analyze meteorological fields for nine cases of mesoscale cloud cluster over South China in May and June, 1980. The results show that the filtered fields are obviously of the mesoscale nature. The distributions of the fields of several elements are related to the locations and intensities of the cloud clusters six hours later.