By introducing levy-lindeberg theorem to raingauge networks planning, the authors obtain a linear relationship between the measurement precision of areal rainfall(relative error or permissible error) and raingauge networks density(average station spacing). The slope of relative error growing is directly proportional to the mean square error of random observation error, inversely proportional to square root of the areal rainfall and region area. Based on simulated rainfall fields and highdensity rainfall dat...