Unearthed bronzes are easily eroded by the external environment due to their perennial burial underground and different kinds of corrosion occur. The presence of "harmful rust" accelerates the corrosion of bronze substrates. Aiming at the common corrosion of loose green rust, the safe cleaning thresholds by the neodymium yttrium aluminum garnet (Nd∶YAG) laser cleaner in dry, wet, and agar gel states are investigated in this paper. The surface morphologies and compositions are characterized by the microscope, in situ Raman spectroscopy, and energy disperse spectroscopy (EDS). The results show that the cleaning threshold in wet state with short free running (SFR) pulse mode is 2.83?8.49 J/cm². The high corrosion removal rate is obtained, which is conformed to the rule of the "no change in the appearance of cultural relics" and the "minimum intervention" in cultural relics protection.