The simulation of seismic wavefield is a precondition for studying the wave response and imaging of collapse columns. However, traditional structured grids are difficult to accurately describe their complex vertical shape and wall rock features, leading to errors in wavefield simulation for irregular collapse column. Therefore, six models of collapse column with different vertical section and wall rock were constructed, and Blossom-Quad method was used to subdivide non-structured quadrilateral body-fitted grids. Then seismic wavefield was simulated by using the Legendre spectral element method and a comparative analysis about wavefield characteristics of different collapse columns was given. The analysis results show that the Blossom-Quad method has high applicability for complex collapse column models, and spectral element method can obtain more accurate seismic wavefield based on this. Diffraction waves are formed at the top, bottom of collapse column and breakpoint of geological interface, and the irregular collapse columns have more complex diffraction waves. The shape of diffraction waves is also affected by the vertical shape of collapse column. When the source is located on both sides of the collapse column, reflection waves form at column wall and the wall morphology is basically consistent with reflection morphology. In addition, when collapse columns cut off the stratum, the stratigraphic reflection appear abnormity such as discontinuity, indentation and amplitude attenuation of events. And these abnormity of wavefield is more obvious in horizontal component than vertical component.