Hybrid improper ferroelectricity (HIF) is a secondary ferroelectric ordering induced by the coupling between oxygen octahedral in-plane rotation and out-of-plane tilt in a metal-oxide containing the perovskite structure units. Investigation of HIF will greatly extend the connotation and denotation of ferroelectric physics and material science, and it is expected to develop the room temperature single phase multiferroic material with large polarization and strong magnetoelectric coupling, owing to its intrinsic characteristic of the electric-field control of magnetism through HIF in magnet. In the present paper, the recent primary progress of HIFs and the multiferroics with Ruddlesden-Popper structures is reviewed, and the perspective of the future development is also presented.