In this paper the mathematical model have been developed for the computation of pressure gradient, viscosity, yield stress and wall shear stress and the influence of stenosis in the rheology of blood, where the blood flow is assumed to behave like a couple stress fluid, peripheral layer plasma (Newtonian fluid) and core layer of suspension of erythrocytes (Non- Newtonian fluid). The non-Newtonian fluid in the core region of the artery is assumed as a Herschel-Bulkley fluid. The resultspredicts that wall shear stress has directly proportional relation to the length of stenosis, yield stress, viscosity and pressure gradient respectively, and inversely proportional relation with the value of powermodel index n. The obtained results for wall shear stress in this paper have been compared to the results obtained by Musad and Khan (2010). It is observed that for the range of the height stenosis 8×10-5 to 10×10-5, the wall shear stress in case of Herschel-Bulkley fluid is considerably lower than these in case of Casson fluid.