Abstract: The wake flow field around the parallel twin cylinders is complex, and a variety of complex wake patterns appear at different spacings. In this paper, based on the finite volume method, a numerical simulation of the flow around two-dimensional parallel cylinders with different spacings at low Reynolds number Re=200 was carried out. The flow field was ana-lyzed by modal comparison. The analysis results show that the proper orthogonal decomposition(POD) method can obtain the main characteristics of the dynamic system in space, and fewer modes contain most of the energy of the flow field. When the distance g=1.5 m, the interference between the upper and lower cylinders is weak, and the wake presents a periodic synchronous and co-directional pattern. When the distance g=0.35 m, the interference between the upper and lower cylinders is strong, and the flow phenomenon is more complicated. The wake presents an alternate flip pattern, and the flow field no longer has obvious periodic regularity. At the same time, the POD method can obtain the main spatial distribution chara-cteristics of the wake flow, with fewer modes containing most of the energy of the flow field, and the wake modal structure with a spacing of g=1.5 m is more compact and orderly than the modal structure with a spacing of g=0.35 m, which is closely related to the wake flow patterns under different spacing g.