This paper aims to present three-dimensional simulation of blood behavior in the system of human coronary arteries. The mathematical model is a set of partial differential equations including continuity equation and Navier-Stokes equations. The pulsatile conditions due to the heart pump during a cardiac cycle is imposed on the boundaries. Computational domain consists of the base of aorta, the left and the right coronary arteries. Finite element method is applied for the solution of the mathematical model Blood flow and temperature distribution in coronary system with normal arteries and stenosed arteries are computed. The results show that the appearance of stenosis reduces blood flow rate in the stenosed artery