In order to research the transformation of potassium in the torrefaction and the release law of subsequent combustion process of straw biomass,corn straw was pretreated in a tubular furnace,and the release rate of potassium and the conversion of different classes of potassium were measured by fractional extraction combined with ICP-AES after torrefaction at different temperature. A multi-point LIBS system was used to measure the release of potassium during the burning of corn straws in real time. The results show that the higher torrefied temperature is,the stronger the activity of organic functional groups is,and the more H2O-soluble potassium is converted into organic potassium. The release of different classes potassium of torrefied samples in the volatilization and the char stage are significantly different in the subsequent combustion. During the combustion of corn straw torrefied at low temperature,the release peak of devolatilization is high and the total amount of devolatilization is large,less is released during char combustion,which is related to potassium enrichment and porosity of samples. The release concentration and release rate of high temperature torrefied corn straw in devolatilization stage are low. In the char combustion stage,the release of more is related to less volatile matter and higher ash. The proportion of H2O-soluble K in corn straw before and after baking is the largest,and the release rate of H2O-soluble K is close to the total K release rate during burning,indicating that the release of H2O-soluble K plays a leading role in the total K release rate.