Abstract: This study addresses the issues of imaging accuracy and defect identification difficulties in the debonding detection in concrete-filled steel tube (CFST) structures, this study conducts parameter optimization for ultrasonic phased array (UPA) based on the total focusing method (TFM). A 3D numerical simulation model of CFST with debonding defects is established, and the contrast metric is adopted as the quantitative evaluation criterion. Through the control variable method, the effects of excitation frequency, aperture width, and element number on TFM imaging quality are analyzed. The results indicate that a central frequency of 1.0 MHz provides optimal imaging contrast while ensuring sufficient penetration depth; an aperture width of 20 mm effectively balances lateral resolution with background texture suppression; and a 32-element configuration satisfies real-time detection requirements while enhancing imaging precision. Laboratory experimental results demonstrate that the developed UPA system can effectively identify debonding defects with a thickness of 0.4 mm. This research provides a valuable reference for equipment parameter configuration in engineering inspections of CFST interface defects.