Abstract: The molecular weight,the rate of glycosylation and the glycosylation site of Ribonuclease B were determined by MALDI TOF MS combined with protease and endo glycosidase digestions.Alpha Cyano 4 hydroxycinnamic acid was used as matrix,and Endoglycosidase F and Glu c were used to digest the glycoprotein respectively.The experimental results indicate that the estabished method is rapid,simple and sensitive.The signal can be obtained at the low PM sample level. The detection abilities can be down to the low level of PM sample.