To achieve highspeed ultrasonic imaging for irregular twolayered medium, one kind of frequency domain synthetic aperture focusing technique (SAFT) based on visual source (VS) technique is proposed. Firstly, VS technique is adopted to construct a series of VS points at the interface of an unknown testing object with irregular twolayered structure. Secondly, the expression of irregular interface is obtained by the interpolation processing with the coordination of VS points. Thirdly, the velocity model is formulated, which represents the velocity distribution in the mesh imaging region according to the expression. Finally, the velocity model is used to accommodate lateral velocity variation for each migration interval during the implementation process of the nonstationary phase shift migration imaging. The performance of the method is evaluated using the convex surface and the sinusoidal curve surface, respectively. Meanwhile, the imaging results and the operation efficiency of the frequency domain VSSAFT are compared with the time domain VSSAFT. Experimental results show that the defect location and the surface shape are displayed accurately in two kinds of VSSAFT images. In the single CPU core condition, the calculation time is only 047～053 s for the frequency domain VSSAFT. However, the time domain VSSAFT need consume 9121～9354 s.