The mechanism and properties of new biocide FA 101 used in industrial cooling water were studied through laboratory static test. Then the influences of different concentration, acidity and alkalinity on the efficacy of new biocide, and the relation of efficacy duration and new biocide concentration were discussed. Meanwhile, comparative tests between FA 101 and isothiazolinone were made. The results showed that biocide FA 101 has preferable effect when pH value is at 6 0~9 0,and the efficiency of killing fungus of biocide FA 101 can reach 94%~99%.