The invention provides a numerically-controlled grinding system for a square box. The numerically-controlled grinding system for the square box comprises a first grinding mechanism, a first driving mechanism, a second grinding mechanism and a second driving mechanism, wherein the first grinding mechanism comprises a first mounting rack, a first sliding rack, a first moving rack, a first rotating shaft and a first grinding wheel; the first driving mechanism comprises a first driving device, a second driving device and a third driving device; the second grinding mechanism comprises a second mounting rack, a second sliding rack, a second moving rack, a second rotating shaft and a second grinding wheel; the second driving mechanism comprises a fourth driving device, a fifth driving device and a sixth driving device. The numerically-controlled grinding system for the square box is simple in structure, convenient to use, stable in structure, and outstanding in grinding effect.