The development in ultrasonic testing of steel plates in Nanyang Hanye Special Steel Co., Ltd. was elaborated. The main defects in nonconformity in ultrasonic flaw detection were summarized as non-metallic inclusion, central segregation, internal crack and so on whose technology reason was analyzed.A series of effective ways was found to solve nonconformity in ultrasonic flaw detection of steel plates such as deposit treatment, overheat control, stacking for slow-cooling and so on, so that we effectively prevented nonconformity in ultrasonic flaw detection from affected the quality of the steel plates.