The invention discloses a cleaning method for a liquid injection hole of a lithium ion power battery. The cleaning method comprises the steps of cleaning the liquid injection hole with laser before laser sealing of the liquid injection hole of the lithium ion power battery, installing a charge coupled device (CCD) photographing detection system on a marker, automatically seeking the liquid injection hole, determining a position of the liquid injection hole, automatically giving out laser, marking and cleaning all surfaces of a sealing part needed to be welded by laser, allowing a crystallization electrolyte, a foreign matter and a surface oxide layer to volatilize at a high temperature during the marking process and to be pumped away with a smoke discharging and dust removal system, and placing a sealing valve for laser welding. The cleaning method has the advantages that manual operation is substituted, electrolyte crystal, the oxide layer and the foreign matter on a surface of the liquid injection hole and around the liquid injection hole all are removed in one time, no fire is exploded during sealing laser welding, the sealing yield is ensured, the efficiency is high, and the cost is low; and the liquid injection hole is automatically sought, automatic cleaning is achieved, the crystallization electrolyte, the foreign matter and the surface oxide layer are volatilized at thehigh temperature during the marking process and are pumped away with the smoke discharging and dust removal system, and a surrounding environment cannot be polluted.