Abstract: An ultrasonic feature scan imaging system used for testing delamination flaw probably existing in the bimetal rotor clad layer was studied and developed. The bimetal rotor with nine column holes could be tested automatically. All the wave train of testing result would be saved in computer for post processing. Various imaging modes, including depth imaging and amplitude imaging, could be used to find delamination flaws accurately and to estimate their size. Imaging experiments for actual work piece was done using the system, and all kinds of feature information were collected. The system was characteristic of high stability and good repeat ability.