Ferromagnetic transition has been generally considered to involve purely an ordering of magnetic moment without any change in the host crystal structure or symmetry,evidenced by a huge wealth of crystal structure data from conventional x-ray diffractometry(XRD).However,the existence of magnetostriction in all known ferromagnetic systems indicates that the magnetic moment is coupled to the crystal lattice; hence there is a possibility that magnetic ordering may cause a change in crystal structure.With the development of high-resolution synchrotron XRD,more and more magnetic transitions have been found to be simultaneously accompanied by structural change.In this article,we review our recent progress on the structural change at ferromagnetic transition,mainly including evidence from the synchrotron XRD for structural change at ferromagnetic transition,a phenomenological theory for crystal structure change upon ferromagnetic transition,magnetic morphotropic phase boundary(MPB)and so on.Two intriguing implications of non-centric symmetry of ferromagnetic phase and first-order nature of ferromagnetic transition are also discussed here.In short,this review is intended to give a self-consistent and logical account of simultaneous structural change at ferromagnetic transition,which may provide new insight for developing highly magneto-responsive materials.