This paper investigated the forming defects causation and related resolving measures by combining numerical method with experimental technique. A practical case of one auto-body panel stamped parts with forming defects was studied in detail. A new approach determining the causation of forming defects and finding out resolving ways was proposed. Firstly, uses numerical method to analyze the characteristics of the whole forming process by dividing the forming process into virtual steps, so as to obtain the forming feature such as stress & strain distribution during the stamping process. Secondly, uses experimental grid method to measure the real plastic strain distribution of the defective area thus to analyze the forming rule of this area. By synthesizing both methods and carrying out extensive analysis, it is possible to make sure the cause of the defects and put out solving scheme further. The study shows that numerical combined with experimental method is an effective way in analyzing and resolving forming defects for auto-body parts.