The particle size distribution, chemical composition, microstructure, thermogravimetric behavior and the slagging and fouling characteristics of the peanut shell ash (PSA) and corncob ash (CCA) prepared by ashing at 600℃ and 815℃ were comprehensively studied by using techniques like laser particle size analyzer (LPSA), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and thermal gravimetric\|differential thermal analysis (TG-DTA). It was presented that ashing temperature had a remarkable effect on the properties. Whereas, it had no obvious effects on the slagging and fouling characteristics. Both the granularity and the total weight loss decreased with the increase of ashing temperature. The contents of K, Na and Cl gradually reduced with the increase of ashing temperature. However, the contents of Si and Ca had no obvious variation. The 600℃ PSA still maintained the original skeleton of peanut shell biomass. The broken degree of 815℃ PSA was much more serious than that of 600℃ PSA. A small amount of SiO2 crystal was found in 815℃ PSA. For CCA, there was an obvious fusion phenomenon in the 600℃ ash while the 815℃ ash presented serious slagging characteristics. For 600℃ biomass ashes, the main weight loss occurred within 300~600℃ and the differential thermal curve showed an intense exothermic peak in this temperature range. It indicated that the soften or melt process of ash was accompanied with the exothermic reaction. For 815℃ CCA, the weight loss between 600~800℃ was considered to be caused by the volatilization of lively alkali metal chloride as well as the decomposition of unstable carbonates when under high temperature.