The reason for fracture and solution: the failure of injection mold, die in use process, because the local stress concentration and crack or fracture of the phenomenon known as the fracture failure. This die failure occurred in parts of more complex geometry, position is generally sharp corners or thin wall cavity. The measures mainly: 1 in the design of plastic parts should be paid attention to in the process; 2 when making a more complex shapes, especially large and medium-sized parts, should try to use high toughness die material molding parts, namely should as far as possible the use of carburized steel, hot work die steel, high carbon alloy tool steel with little or no heat treatment of poor performance. In addition, should also be reasonable design of die structure, where necessary, insert structure adopted in the prone to fracture site, avoid the whole die due to failure and premature retirement.