The application provides a motion control method and a motion control system for a detecting device for a radioactive solid waste bucket. The method comprises the following steps: dividing the radioactive solid waste bucket into a plurality of voxels and dividing the radioactive solid waste bucket into a plurality of detection levels along an axial direction; selecting an initial detection level, and determining an intersection point which passes a circle center of the initial detection level and is vertically intersected with a vertical surface as an initial detection position; calculating initial detection positions of a radioactive source and a detector according to the initial detection position; calculating a motion curve of the radioactive solid waste bucket according to the initial detection position and the mass of the radioactive solid waste bucket; calculating motion curves of the radioactive source and the detector according to the motion curve of the radioactive solid waste bucket and the initial detection positions of the radioactive source and the detector; controlling a waste bucket horizontal motion mechanism, a radioactive source vertical motion mechanism, a detector vertical motion mechanism and a detector horizontal motion mechanism to synchronously operate according to all the motion curves; detecting radionuclide in the radioactive solid waste bucket. According to the technical scheme provided by application, the coordination and the detection efficiency of all mechanisms in the detecting device can be improved.