Modal curvature difference (MCD) method is an effective damage detection technique for beams but not very feasible for plane member structures, because the MCD of each member is difficult to calculate with the structural modal shapes which are expressed in a global coordinate system. By improving MCD method, this paper develops a general and convenient damage detection method for plane member structures. The new method introduces coordinate transformation technique to settle the calculation difficulty of MCD. To validate the availability of the method, the finite element damage model of a typical structure is built up, and detection effects on the case of single member damage and multiple member damages are studied respectively. The results show that the improved method is especially suitable for the damage detection of plane member structures.