Many factors affect the flow of blood in the arteries and other small vessels among which are the diameters of the various vessels, the viscosity of the blood and various constituents of the blood. People with the HbS type of red blood cell have their cell sickle. The present study used a one-dimension model of flow in the arteries to investigate the effect of increase viscosity on small pressure disturbance and on the arterial compliance and the sequence of shock. We deduced that increase viscosity which all sickle cell patient are prone to leads to reduced flow and hampers the distribution of oxygen to essential areas of the body. The higher the viscosity the more like the crisis will occur.