To investigate the impact of rectangular section sizes on the stability of roadway surrounding rocks, the east wing transportation main roadway of Baijiahaizi Mine was selected as the research object. Utilizing numerical simulation software, the plastic zone of the surrounding rocks, vertical stress, horizontal stress, and deformation of the surrounding rocks under different width-to-height ratios with a cross-sectional area of approximately 20 m2 were simulated and analyzed. The results indicated that as the width-to-height ratio increased, the range of the plastic zone of the surrounding rocks continuously expanded; the larger the width-to-height ratio, the greater the peak value of the vertical stress, while the peak value of the horizontal stress became smaller; as the width-to-height ratio increased, the vertical displacement of the roadway continuously rose, and the horizontal displacement showed a trend of initially increasing and then decreasing.