Welding Continuous Cooling Transformation (CCT) graph reflects the relationship between microstructure, hardness of steel heat-affected zone (HAZ), weld and welding cooling rate continuous cooling from high temperature, and it is the basic to select welding material, determine the optimum welding technology, relieve welding cracks and lay down standard of past heat treatment. Welding technological parameters determine welding cooling rate, and the rate determines microstructure, hardness of steel HAZ and weld, therefore we can calculate microstructure according to known welding technological parameters and optimum parameters according to wanted properties based on CCT graph. The system combines CAD and welding techniques, the welding CCT graphs are made into drawing blocks at the platform of AutoCAD, the important data of welding CCT are made into database, they are transferred and managed by Access. Based on Active Automation techniques using Visual Basic, AutoCAD graph base are transferred and data of welding CCT can be inquired and dynamically added to the base. The system has realized the prediction of welding structure and properties and optimizing welding technology.