An online high-pressure water-jet blasting surface cleaning system comprises a high pressure water feed mechanism, an abrasive material feed mechanism and a spray nozzle. The high pressure water feed mechanism and the abrasive material feed mechanism are communicated with an input end of the spray nozzle, an abrasive material collecting pit is arranged below the spray nozzle, an output end of the abrasive material collecting pit is divided into two paths, one path is connected with an input end of an abrasive material sorting device by an abrasive material cyclical feeding device and a pipeline, and the other path is connected with an input end of a waste water treatment circulating mechanism by a pipeline, an output end of the waste water treatment circulating mechanism is connected with the high pressure water feed mechanism by a pipeline, an output end of the abrasive material sorting device is divided into two paths, one path is connected with the abrasive material feed mechanism, and the other path is connected with a slag collection barrel by a pipeline. The online high-pressure water-jet blasting surface cleaning system has the advantages of simple and compact structure, low energy consumption, good environmental protection, good operational reliability and stability, and recycled water and abrasive materials.