The invention discloses a numerical control milling machine spindle box structure. The numerical control milling machine spindle box structure comprises a first box body, a second box body, a guide rail and a sliding block; the rear end face of the first box body is arranged on a stand column, the guide rail and the second box body are arranged on the front end face of the first box body, one endof the sliding block is fixed to the second box body, the other end of the sliding block is connected with the guide rail, and the sliding block slides along the guide rail along with rotation of thesecond box body. Through connection of the guide rail and the sliding block, a spindle box has the higher overturning-prevention capacity, the whole structural rigidity of the spindle box can be improved, meanwhile, avoiding of a tool fluttering condition is assisted, the surface roughness and the waviness of blades are reduced, machine tool machining precision is improved, and the blade machiningquality is improved.