Spatial heterogeneity is a very important issue in studying functions and processes of ecological systems at various scales. Semivariogram analysis is an effective technique to summarize spatial data,and quantification of spatial het-erogeneity. In this paper, we propose some prmciples to use semivariograms to characterize and compare spatial heterogene ity of ecological systems and use an example of old growth forests of Korean pine to demonstrate these prmciples and to dis-cuss its charactcristics of spatial heterogeneity. Spatial heterogeneity is a very important issue in studying functions and processes of ecological systems at various scales. Semivariogram analysis is an effective technique to summarize spatial data, and quantification of spatial het-erogeneity. In this paper, we propose some prmciples to use semivariograms to characterize and compare spatial heterogeneity of ecological systems and use an example of old growth forests of Korean pine to demonstrate these prmciples and to dis-cuss its charactcristics of spatial heterogeneity.