Reentry vehicle often uses reaction control system for providing necessary critical forces during reentry. The effect of lateral jet due to reaction control system on aerodynamic characteristics especially stability aspect of a reentry vehicle has been investigated .CFD analysis of the interaction of a lateral jet on Leeward side has been investigated on a reentry body with a circular sonic air jet injected normally in to hypersonic flow from the body surface. A systematic numerical analysis for a lateral jet interaction was performed at angles of attack 0, 2, 5, 8, and 10 degrees at free stream Mach number 8.1. The methodology has also be verified by comparing the pressure distribution at an angle of attack of 20 degrees with experimental data. The effect of lateral jet on aerodynamic characteristic has been studied by comparing the variation of aerodynamic characteristic along the length with and without lateral jet. The aerodynamic coefficients variation of aerodynamic characteristics along the axial length is studied with and without jet. Force coefficients, pitching moment coefficient and centre of pressure are studied with jet and without jet conditions by varying the angle of attack. The Mach contours, velocity vectors and path lines represent the effect of lateral jet. The computational results are validated here to compare the experimental results obtained from open literature.