A new method to improve the passing performance of monorail train driving on a curve by adjusting the width of monorail beams is proposed. Equations for deformation of steering wheel and stabilizing wheel with respect to the contact relationship between monorail beams and trains are derived by geometric analysis. Then two kinds of adjustment schemes are proposed, equal width adjustment method and unequal width adjustment method. A curved guide way of radius 100 m is taken for the example to verify the validity of the improved method by comparing the tire deformation of monorail train driving on the beams before and after the adjustment of width. The results show that the improved adjustment method for the width of monorail beam is efficient to reduce tire deformation when the monorail train travels on a curve. For the guide way of radius 100 m, width of the beams should be reduced by 7 mm when the equal width adjustment method is adopted. When the unequal width adjustment method is adopted, the width of monorail beams at the position of steering wheel carriageway and stabilizing wheel carriageway should be reduced by 10 mm and 5 mm, respectively.