Abstract: The study on the thermal tolerance of marine organisms in the receiving water body of thermal discharge is an essential part and important basis for establishing and perfecting the assessment of environmental impact of thermal discharge and its emission control standards.The adjacent waters of four typical coastal nuclear power plants (Hongyanhe, Shidao bay, Sanmen and Taishan NPP) were chosen as the research objects.The Chaeturichthys stigmatias was selected as the wide-area fish in the four typical coastal sites.The CTM (critical temperature maximum) tests and UILT₅₀ (upper incipient lethal temperature) tests of the Chaeturichthys stigmatias were carried out.According to the results of these two kinds of tests, the rates of temperature rise had different effects on the CTM value of Chaeturichthys stigmatias captured from different sea areas in different seasons; the CTM and 24-hour UILT₅₀ were in direct proportion to the initial temperature of the test; except for the rates of temperature rise and the initial temperatures of the tests, other key factors, such as the individual size and the growth stages of the species, were also the main influencing factors of the CTM value of the same species; the CTM of Chaeturichthys stigmatias was higher than its 24-hour UILT₅₀ under the same condition.