Abstract: To study the fouling and slagging properties of fly ash from combustion of Xinjiang high alkali coal, XRF and SEM-EDX analysis were carried out to ash samples taken from various heating surfaces in a 300 MW subcritical boiler burning high alkali coal. Results show that in the gas temperature range of 800-1 100 ℃, mass fractions of CaO, MgO and SO3 in ash samples are relatively high; whereas for in temperature range of 600-800 ℃, mass fractions of Na2O, Fe2O3 and SO3 are relatively high, in which case serious fouling on high-temperature convection heating surfaces is caused by Na2SO4, CaSO4 and NaFeSO4 during combustion of high alkali coal. For locations where the gas temperature is in the range of 669-915 ℃, both the initial melting temperature of ash samples and corresponding liquid slag ratio are higher than those in other places. Na2SO4 particles with sizes of 2-4 μm rich in Na and S are found to stick on surface of ash sample C, which at high temperatures have high sticky properties and low melting temperatures, and therefore may lead to serious fouling problems.