Mode I fracture is one of three primary macroscopic fracture modes, which is the most common tensile fracture. The mode I crack propagates in a direction normal to the applied stress. Micro cracks, voids, inclusions, segregation and second phases in materials are unavoidable, which affect directly the strength of materials. Hence, stress fields in mode I crack and its tip became focus of this fracture type. Gurson, Tvergaad and Needleman (GTN) developed the constitutive model which has taken into account voids, micro cracks, inclusion, etc. in materials. This model reasonably illustrated the brittle fracture to some extend. Numerical analysis of infinite plate with mode I crack employed GTN model has been conducted and completed in this paper with the help of FEM software ABAQUS. The length of crack was 20mm (a=20mm) and the curvature in the tip of crack was r=10(-5) m. The dimensions of plate which subjected to uniform stress at two ends were 40a long and 20a wide. The material of plate was typical elastic-plastic materials. The distributions of stresses, strains and values of damage at the tip of crack was obtained by the FEM software. The process of propagation of crack was completely simulated by the method of element failure.