Microcrystalline cellulose (MCC) was activation treated by amine, water and ultrasonic respectively. The dissolve time in NaOH-Urea-Thiourea solution, degree of polymerization (DP), solubility, the surface of fiber, crystallinity and effect on molecule hydrogen bonding of MCC before and after activation were studied. The result showed that ultrasonic activation is better than the other two activation methods, which is more convenient to improve the dissolvability of MCC with treating power from 60 to 99 percent and treating time from 60 to 120 minutes.