The centre of form is the geometrical centre of the cross-section of a member and is related only to the shape and size of the cross-section.But the axis of symmetry of the cross-section of the centre of form in the axis of symmetry, double axis of symmetry cross-section of the centre of form in the intersection of the two axes of symmetry.Shear centre: when the external force (mainly transverse force) through the shear centre, the member (mainly beams) on the cross-section will not produce additional shear stress.Axisymmetric section of its shear centre in the axis of symmetry, but with the form of the centre in different sides, double axisymmetric section of its shear centre is also in the intersection of the two axes of symmetry.