Abstract: Late June and early July each year are the peak periods of Cryptocaryon irritans infection of Pseudosiaena crocea cultivated along the coastline of Fujian province. In order to investigate the causes of massive death of sick Pseudosiaena crocea, we carried out an experiment on tolerance of Pseudosiaena crocea suffered from Cryptocaryon irritans disease to low dissolved oxygen. The result showed that the fish suffered from more serious disease, even floated head and died in large number, the dissolved oxygen in water was higher and the oxygen consumption rate was lower. The choke point and oxygen consumption rate for healthy fish were 2.58 mg/L and 332.4 mg/kg·h^-1 respectively, and those of fish infected diseases in the degree of "+++" were 3.83 mg/L and 196.0 mg/kg·h^-1 respectively. Combining the experimental results with situation of Pseudosiaena crocea culture production, we concluded that the decreasing tolerance of Pseudosiaena crocea suffered from Cryptocaryon irritans disease to low dissolved oxygen easily leaded to explosive death in a great deal.