The properties and applications of the photorefractive two-wave coupling in con gruent SBN:Cr(Sr0.61Ba0.39Nb2O.6:Cr)crystal under external dc e lectric field are experimentally investigated in this paper.The variation of the intensity gain coefficient of the two-wave coupling with the external field is analyzed,and the measurement results are presented.It is found that the photore fractive two-wave coupling gain and response rapidity can be both increased,by applying appropriate external electric field to the crystal.Further study indica tes this electric response property of SBN:Cr crystal is useful to some applicat ions,such as improving the image edge-enhancement and the image edge-enhanceme nt joint-transform correlator based on the nonlinear energy transfer of photore fractive two-wave coupling in the crystal.