Abstract: In this paper, the ultrasonic phased array frequency-wavenumber domain total focusing method was applied to 304 stainless steel sheet metal layered defect detection. Two kinds of models of phased array probe were used, to detect 1 mm and 3 mm thickness of sheet metal layered defect, and the conventional time domain total focusing method and frequency-wavenumber domain total focusing method imaging quality of two kinds of algorithm were compared. The research results show that total focusing method algorithms based on time domain and frequency-wavenumber domain can detect layered defects of thin metal plates. As compared with conventional time domain total focusing method imaging, the frequency-wavenumber domain total focusing method imaging detection has high resolution, smaller artifact areas and other advantages.