Abstract: In this paper, corn stalks with different granularities were treated by Phanerochaete chrysosporium, and discussed the decomposition characteristics of the stalk by the measurement of the decomposition rates of stalk and lignin, and the total amount of organic matters, humic acid, H/F, carboxyl and phenolic hydroxyl groups. The results showed that the quantities of the stalk, organic matter, and lignin gradually decreased during the decomposition process. There was a significant relationship between the decomposition rate and time and the particle size of the stalk. Furthermore, humic degree increased with H/F increasing, while the content of phenolic hydroxyl decreased, and carboxyl content increased. These results indicated the decomposition process of the stalk is an oxidation one that phenolic hydroxyl is oxidized to be carboxyl.