Abstract: In order to explore the potassium supply capacity and releasing characteristics of different tobacco-planting soils originated from different parent materials in Hunan Province,tobacco-planting soils originated from 4 representative parent materials were surveyed.The results showed that:the release amount of potassium mainly depends on the specially absorbed potassium,and is relatively less from non-exchangeable potassium;There are significantly positive correlations between soluble potassium and the initial release rate or the rate of semi release potassium,and between absorbed potassium and the initial release rate or the rate of semi release potassium.In despite of the limited soil potassium supplying capacity,soils derived from the Quaternary Red Soil parent material maintained high potassium initial rates and available potassium levels,and soils originated from the limestone parent material showed higher specially absorbed potassium which provides relatively stable potassium sources and has better potassium capacity;By comparison,soils originated from the purple slate and plate shale parent materials have larger potassium storage capacity and potassium supplying potential,but the available potassium content is relatively low,and the amount and supply intensity level of potassium is limited.Soils derived from the limestone parent material were top ranked in potassium supplying capacity,followed by Quaternary Red Soil,late shale,and purple slate.