Abstract: Feasibility study on phased array ultrasonic testing method was carried out for insulation materials of epoxy casting products by simulating defects. Firstly, the sound velocity of the material at different temperatures was measured using the actual measurement method to set the focusing rule and calibrate the measurement curve; secondly, after calibrating the curve, different gains were selected and the depth of the prefabricated defect was measured using a straight probe and an oblique probe, respectively; finally, based on the measurement results, the detection limit, detection accuracy, signal-to-noise ratio, and stability of the detection data were analyzed to demonstrate the feasibility of this method. The experimental results showed that phased array ultrasonic testing had strong penetration ability and can complete the testing of epoxy casting products, but it required high requirements for testing personnel, took a long time for testing, and had low efficiency.