Abstract: In response to the problem of difficulty detecting the combination of the engine connecting rod and the connecting rod small end bushing, the propagation process of sound field and the characteristics of echo signal during ultrasonic detection of the fit degree of connecting rod bushing were studied by finite element simulation and test analysis. The results show that under the connection of defect and no defect, the ultrasonic echo signal will produce two reflected echoes, and the amplitude of the second reflected echo is obviously different. The recursive analysis of the echo signal shows that when the interface is defective, the return signal recursive plot will present a white cross-striped band. Further research through recurrence quantification analysis finds that the obvious difference of the value of ratio when there are defects and non-defects at the interface of the bushing, which can effectively distinguish whether the defect exists.