Abstract: Raindrop spectrum observation is a key work to research characteristics of natural precipitation and simulated precipitation and design equipment of rainfall simulator precipitation.Combining plotting software of computer with traditional Color-spot method,a new method for raindrop diameter measuring and data processing was probed into.The method decreased the lower limit of measurement from 1.0?mm to 0.2?mm,it(enlarged) the measure range as 10 times as before,and reduced the work quantity largely.The correlation formula between raindrop diameter and Color-plot diameter was educed,whose applicability and advantages were tested.Results showed that the formula would be the best when raindrop spectrum was analyzed by improved Color-spot method.