Platelet activation and functional changes were investigated in acute lymphoblastic leukemia (ALL) to provide the basis for early diagnosis and evaluation of curative effect. Platelet parameters, immature platelet fraction (IPF%), immature platelet count (IPC), P-selectin (CD62p) (PAC-1) expression were detected in ALL, ALL-complete remission-induced (CR1), and normal groups with an automatic blood cell analyzer and flow cytometer. CD62p and PAC-1 were higher in the ALL group before adenosine-5-diphosphate (ADP) activation than in the normal group (P 0.05). PDW did not differ statistically among all groups (P > 0.05). IPF% and IPC values were higher and lower in the ALL group than in normal and ALL-CR1 groups (P 0.05). Therefore, ALL patients demonstrate platelet activation and platelet dysfunction; platelet parameters and membrane glycoprotein expression can be used to evaluate the effect of ALL.