A plot (20 m×30 m) was delineated for study in the Maolan karst virgin forest, containing 7 types of microhabitats: rocky surface, soil surface, rocky soil surface, rocky gullies, rocky crevices, stone pits and stone caves.The soil organic carbon (SOC) contents in the plot ranged from 40.1 g kg^-1 to 203.5 g kg^-1.The variation coefficients of SOC contents of the plot and the microhabitats were 43% and 41%, respectively, 22%～42% between microhabitats of the same, and 14%～57% within a microhabitat, suggesting high spatial variation of the SOC contents in the plot.In order to improve comparability of the data available for the study of soil degradation in the karst ecosystem, a representative sampling method is advanced for collecting samples in a sampling site formed of sampling points of the same microhabitat, which is delineated based on soil area weight.It goes like this: select several types of microhabitats whose respective sum of land areas exceeds 95% of the total soil area of the sample plot, determine quantity of the soil sample of each microhabitat that forms the representative soil sample of the plot by area weight, and the soil sample of each selected microhabitat is mixed out of soil samples from land patches of the same type of microhabitat, and their quantities are determined by area weight.Using this method, the surface area-weighted value of the SOC content in this plot was figured out to be 92.1 g kg^-1.