Abstract: The paper introduces the application of ultrasonic detection in practice, including its principles and components Selection of the best conditions for detecting copper casting is also explained in this paper.In order to raise signal-to-noise ratio(SNR) and get a better result in the testing, various ultrasonic testing techniques and methods are presented and compared, so the special techniques of inspection for the thick-wall copper casting with coarse grain is settled down and the reasonable parameters of probes are obtained by comparing different kinds of probe ( including different frequency, different piezoelectric wafer etc.) in testing.