Abstract: This paper is concerned with the thickness-twist wavespropagating in an infinite magneto-electro-elastic bi-material plate. Theupper and lower surfaces of the plate are assumed to be mechanically free,electrically open and magnetically closed. Based on the fully coupledmagneto-electro-elastic constitutive relations, the general solutions of thethickness-twist waves are first derived. Then the frequency equations areobtained by using the boundary conditions and interfacial conditions. As anexample, for the propagation of the thickness-twist waves in the bi-materialplate consisting of BaTiO_3 and CoFe_2O_4, the distributions ofthe displacement, electrical potential and magnetic potential are obtained.The dependence of the number of trapped modes on the geometric size is alsogiven. The theoertical results are useful for the design of plateresonators, filters and acoustic wave devices with magneto-electric effect.