Rubber-covered pinch rolls are used in the cold rolling shops for feeding the steel coils into the product line. These rolls only provide required force for pinching the steel strip and have no effect on thickness and surface precision. After a short working period (almost 3 to 6 months), the rubber cover of the pinch rolls fails due to rupture. The main aim of this research was to find the best type of compound among polyurethane compounds. In order to test the compounds, a semi full scale test machine was developed. Then several tests were set up to measure effect of each load. It should be mentioned that there were two main mechanical loads on PU layer of the pinch roll. A normal load that provided by two hydraulic actuators and affect on both end of the rolls and a tensile load that imposed by “pay off reel” on steel strip that was connected with rubber cover. First normal load was imposed to evaluate the effect of this force solitarily to find maximum load and rotational velocity that can be applied to the system. Because in cyclic loading, hysteresys phenomena occurs and result in material warming, normal load and rotational velocity are limited. In next test in order to must simulate the pay off reel tensile load, a reverse moment on upper roll is applied by a gear pump. Unfortunately this method failed because of hydraulic system and low power of electrical motors.A successful test was set up and tested by adding third roll that apply tension to the rubber belt which was manufactured by a closed seamless die.Numerical analysis of each test was performed by the powerful finite element software (ABAQUS). Eventually these results were obtained: 1. The higher the rubber hardness, the more the fracture strength against crack growth. For example rubber with 90 Shore A hardness, ruptured later than one with 85 Shore A. 2. Using data obtained from experimental results (the cycles that each rubber belt with determined hardness under loading condition endures until ruptures) and also parameters calculated from software analyzing process (J-integral values), mechanical crack growth constants were calculated for each rubber. 3. Theoretically mechanical crack growth initiates when J 40 j/m 2 that is confirmed with test and real pinch roll. 4. With consideration to numerical results Mode I loading (i.e. Opening Mode) is distinguished to have the most effect on fatigue crack growth.Key Words Fracture Mechanics, Rubber, Pinch Roll, J-Integral, Crack Growth