Abstract: For the character of composite layer structure of the Babbitt alloy and steel, the manual ultrasonic method and feature scan imaging method were adopted to study the detection of composite layer .The manual ultrasonic method adopts single straight probe or twin straight probe. This method compares and evaluates the quality of composition by the bottom echo amplitude and the binding layer interface echo amplitude. The feature scan imaging method adopts focused probe. This method makes use of the amplitude change of binding layer interface echo and the features of the multiple echoes, and at the same time it shows the features of the defect with intuitive and credible result. The latter method is more convenient and feasible for the quality evaluation of the thin Babbitt alloy and steel composite layer.