Leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicle. Originally called a laminated or carriage spring, and sometimes referred to as a semi- elliptical spring or cart sprig. For uniform distribution of bending stress during the loading condition both full length and graduated leaf springs are clamp together and initially forged in a curved shape for initial residual stress. At the time of maximum loading all leaves become straight. This type of spring is called conventional leaf spring. One more concept of stress distribution has been generated that is with the change in thickness of spring in both full length as well as graduated leaves. This type of spring is called parabolic leaf spring. This research is to analyze the study of change in distribution of stress with respect to the length and thickness of leaves. Author has visited JAMNA AUTO INDUSTRIES LTD. MALANPUR to analyze the stress distribution in both type of spring. Collecting data from industry Author has examine the stresses as well as deflection keeping same independent variables of both spring using SOLIDWORKS SOFTWARE. Analyzing the results Author found that parabolic leaf spring is better than the conventional leaf spring suspension system in heavy vehicle.