The invention discloses an acidizing fluid for green algae and a disease infected cell in porphyra haitanensis cultivation and a treating method thereof. A solvent for the acidizing fluid is clean seawater, and solute for the acidizing fluid is at least one of hydrochloric acid and citric acid, wherein the concentration expressed in percentage by weight of the solute in the acidizing fluid is 0.3to 1.5 percent. The green algae and the disease infected cell can be quickly killed by a treating method of preparing the acidizing fluid, shipping, dipping for 15 to 20 seconds and rinsing, killing effect is better, the killing rate is over 90 percent, and the influence on the growth of the porphyra haitanensis is less. The treating method has the advantages of no restriction of natural condition, labor intensity reduction and the like.