The traditional design method of machine tool column easily leads to material redundancy and it is difficult to achieve the best structural efficiency. A bionic method is proposed, bamboo was used as the biological archetype, to design the column structure of an extra-heavy duty CNC boring and milling machine. The macroscopical and microscopic structural characteristic and the mechanical property of the bamboo are analyzed, and the intrinsic relationship between the microstructure and mechanical properties is obtained. The column is designed as cylindrical structure firstly, and the relationship between the number of transverse ribs and the whole bending deformation is ascertained. The transverse ribs are designed for cylindrical structure .By evolving the cylindrical member, A, B two kinds of bionic column are designed and compared. The specific stiffness of B type structure is increased 10.9% and its overall performance is better than the A. So the B scheme is selected as the final bionic structure of the column.