In this research, we report the novel design, fabrication and testing of an assembled comb-drive XYZ-microstage that produces highly decoupled motions into X-, Y-, and Z-directions for the three-dimensional (3D) scanning stage of magnetic resonance force microscopy. The XYZ-microstage based on assembling technology consists of three separated parts, i.e., a comb-drive XY-microstage, two comb-drive Z-microstages and a bottom silicon base substrate. The separated parts are assembled together by using micro manipulators and a guide block of stainless steel. It is demonstrated that the assembled XYZ-microstage can achieve large displacements of 25.2 µm in X direction, 20.4 µm in Y direction and 58.5 µm in Z direction.