This paper studies the influence of temperature and corn straw content on release and transformation of potassium during coal and corn straw co-combustion. The results indicate when the corn straw content was lower, released K decreased due to the reactions of KCI with Fe and Ti forming K2O center dot Fe2O3 and K2TiO3. When the corn straw content was 80 wt%, from 600 degrees C to 1100 degrees C, the release of KCI(g) improved. K existed in ashes as K2SO4 or alumina-silicates. With temperature increasing, the K2SO4 decreased, and the KAISiO(4), KAISi(3)O(8), and KAISiO(6) increased especially between 900 and 1100 degrees C.