Abstract: In order to analyze the effect mechanism of circularization on the winding characteristics of the forced vibrating square column at low Reynolds number, the secondary development of Ansys Fluent software was carried out to program the periodic forced vibration of the column, that is, the DEFINE_ CG_MOTION macro in the user-defined function (UDF) was used, and the computational domain of the flow field was divided into some regions in order to realize the forced vibration of the column by using the dynamic layer method in the dynamic grid technique, so as to realize the simulation of the fluid-solid coupling of the column-wound flow field. At Reynolds number Re = 200, considering the influence of different rounding angles of the square column cross-section, numerical simulation was made for the flow around five forced vibration square columns with rounded corners r/D = 1/2, 1/4, 1/5, 1/8 and 0 under uniform flow, and the variation laws of the drag coefficient, eddy volume and locking interval of the forced vibrating square column under these five parameters were analyzed to clarify the effect mechanism of circularization on the stability of the forced vibrating square column. It is shown that the lift and resistance coefficients of the rounded square column are significantly reduced with increasing rounded angle compared with the sharp-angled square column; the vortex shedding mode of the rounded square column under low amplitude ratio is 2S mode, and the vortex trails become narrower; the locking interval range is basically symmetric about F = 1, and the trend of the locking interval is similar to that of the cylinder.