A tunnel is an underground passageway used for foot or vehicular road traffic, for rail traffic, or for a canal. Earth Retention System i.e. the side concrete wall of cut and cover method for tunnel construction is studied here. The research work is conducted to compare the internal force of side wall computed by conventional method and 3-D computer model result. To achieve the objective, 3-D computer modeling of the whole system, subsequent analysis and result interpretation was performed using the software STAAD Pro. To check the quality of the computer results it is compared with the conventional analysis method inspired by Peck. Finally from the comparison of computer aided assessment and manual calculation, it is revealed that conventional calculation is in good agreement with computer aided assessment. Computer aided assessment should be adapted for detail analysis to get deflection, variation of bending moment on different strip etc. However their suitability varies depending on individual case and some perimeter like time, budget etc.