Abstract : Von Willebrand Factor (vWF) is a multimeric glycoprotein that functions as bridge between platelets and subendothelial tissue, also acts as a carrier of factor VIII. Meanwhile, vWD, a hereditary deficiency of vWF is the most frequent congenital human bleeding disorder that can be classified as type I, II, and III. It has been known that vWF concentration is affected by ABO blood group. The aim of this study is to determine reference value of vWF activities in Indonesian peoples. A cross-sectional study was conducted with 60 subjects of each O blood group and non-O blood group. The activities of vWF were determined by immune-turbidimetric method using Innovance VWF Ac Reagent and Sysmex CS-2100i coagulometer. The measurement principle was an increased turbidity due to agglutination after the addition of polystyrene particle coated with anti GP1b and recombinant GP1b (two gain-of-function mutations included) that bound to the antibody as well as to the vWF of the sample. The reference value of vWF activities in O blood group was 24.2% - 125.4% while in non-O blood group was 37.7% - 166.1%. There was a significant difference between vWF activities in the two groups (p < 0.005). Taken together, our study concluded that the vWF activities of blood group was significantly lower than non-O blood group.