Magnetic drug targeting is a new way to treat cancerous glands and occluded arteries. In this method, by connecting magnetic particles in nano and micro-scale to drugs and cells and injecting them into the body, it is possible to direct them to the target zone by applying an external magnetic field, in that case the concentration of drug and how long it stays around the target tissue increases. This method prevents the drug from spreading in the body and damaging other healthy tissues, so reducing side effects and increasing treatment efficiency are the advantages of this new method. In the present study, endothelial cells containing magnetic particles were injected into the occluded coronary artery in the presence of an external magnetic field. According to research, injecting endothelial cells into the occluded arteries regenerates the vessel wall and restores its flexibility. The aim of this study is investigating the effect of occlusion percentage and chord length on particle capture efficiency. First, the effect of magnetic field on blood flow is investigated. Blood reacts to a magnetic field due to the presence of red blood cells. The purpose of this section is finding a safe magnetic field so that blood flow changes are within acceptable range. The parameters studied in this section are fluid pressure on the artery wall and wall shear stress. After selecting the desired field, in the second part, cells containing magnetic particles are injected into the artery. The purpose of this section is to investigate the particles capture efficiency under various conditions. In this section the effect of magnetic field strength, mass of the injected magnetic particles, time of particles injection into the artery, the percentage and the chord length of the occlusion on the capture efficiency is studied. Numerical simulation is done in Ansys-Fluent software using finite volume method. Fluid flow is laminar and blood is modeled as an incompressible, non-Newtonian. Pulsatile velocity applied at the artery inlet according to the real flow of coronary artery and pulsatile pressure applied at the outlet during a period of cardiac cycle. The artery is also modeled as rigid and elastic. The results show that the presence of magnetic field increases the wall shear stress and pressure for the deoxygenated blood and decreases them for the oxygenated blood. Also, with increasing percentage of occlusion, the amount of flow field changes decreases. By comparing the results, the magnetic number Mn=2.5 was chosen as the magnetic field that changes the blood flow in the safe range. In the second part, endothelial cells containing magnetic particles were injected. The results of this section show that the particle capture efficiency is directly related to the magnetic field strength and mass of magnetic particles injected into each cell and is inversely related to the percentage and chord length of occlusion. These results are true for both rigid and elastic models. By comparing the particle capture efficiency under the same conditions for both rigid and elastic artery, it was observed that the capture efficiency is higher for the elastic one. Keywords: Drug Targeting, External Magnetic Field, Magnetic particles, Coronary Artery, Capture Efficiency