Abstract: By using the method of Polar Ordination, herb community in the Karst area was ordered. The correlation between the coverage of herb vegetation and soil nutrient index was analyzed. The results indicated that the available potassium in the soil was the main factor that limited the distribution of herb community in this area. The coverage was direct correlated to the total potassium, hydrolysable nitrogen and available phosphonium in the soil, also significantly direct correlated to the available potassium in the soil with the coefficient of correlation 0.96. The coverage increased rapidly with the increasing of the available potassium, however, when the amount of available potassium in the soil reached 14834 mg/kg, the growth rate decreased sharply and finally asymptotically flatted.