The majority of acute ischemic events are caused by plaque rupture and ensuing thrombosis. Early evaluation and continuous monitoring of a plaque's vulnerability are critical for reducing the risk of catastrophic cardio-cerebral events and mortality and morbidity of atherosclerotic cardiovascular diseases. Many studies have suggested that increased stress in the fibrous cap of atherosclerotic plaque is the key factor triggers a plaque rupture directly. In this study, we investigate the influence of the blood viscosity and bulk modulus of plaque compositions on the stress distribution in the fibrous cap, by simulating the fluid-structure interaction using COMSOL Multiphysics 3.5a. Our results indicated that, when the thickness of fibrous cap, the degree of luminal stenosis, and the other conditions were fixed, an increase of blood viscosity and a decrease of bulk modulus of lipid core caused shear stresses in all directions and normal stress along the inflow direction to increase. It can be inferred that the increase of blood viscosity and decrease of bulk modulus of lipid core may increase the risk of plaque rupture and then may lead to acute CV events. The simulation results agreed with the previous clinical/experimental studies that indicate that blood viscosity was a major risk factor for ischemic heart disease and soft lipid core was more susceptible to plaque rupture.