In order to solve the problem that three-dimensional imaging result with real data of broadband mono-pulse radar cannot be displayed directly, an expressive method using visual modality in plane was studied. The visual modality in plane is the projection of target structure which was obtained by hypothetic people's eyes when they observed target according with direction of radar beam. In order to obtain the expression with visual modality in plane, firstly, the method for calculating direction of radar beam from real data was given and the necessity for obtaining the beam direction was analyzed by considering the exact estimation of target's size. Secondly, under the basis of having obtained the direction of beam, a new reference frame was formed according to the plane for projection and the method of coordinate rotation from reference frame in radar observation to new reference frame was also presented. In the end, three-dimensional imaging results of some real data for planes in civil aviation were presented with projection in reference frame in radar observation and visual modality in plane in new reference frame respectively, the comparison between two kinds of expression brings forth the value of denotation by visual modality in plane for acquisition of characteristic.