Taking the column of YK7380 forming grinding machine as the research object, the method of improving the low order modal characteristics of the column by adding weight was presented. Comparing the modal characteristics of column before and after equiping the counterweight, it is found that after equiping the counterweight, the natural frequency and comprehensive deformation of the column are declined, vibration mode is also changed, and especially for the fourth order modal, the vibration modal is shifted. The research result shows that the improvement measure by adding counterweight is effective, and this method provides a direction for the low order modal research in column.