Platelets play a major role in the maintenance of endothelial integrity and hemostasis. Exposure of platelets to physical stress such as flow-induced shear stress leads to platelet aggregation, which are accelerated in the presence of exogenous agonists. In this study, we have designed a simple and rapid method for measuring the decrease of blood velocity due to the platelet aggregation and the normalized distance of blood in the microchannel. To evaluate the influence of blood flow on platelet aggregation, ADP and collagen were used as agonists and microfluidic device was made from glass acryl, and double adhesive tape. Our device is expected to be capable of distinguishing the pharmacological effects of various antiplatelet agents under physiological shear rate condition.