A method and a system are disclosed for performing fever triage. At first, a thermal image-detecting unit is used to detect a testee at a time-point and a position so as to form thermal image data. Meanwhile, a visible light image-detecting unit is used to detect the testee at the same time-point and position so as to form visible light image data. Thereafter, thermal image data are analyzed to determine if at least one fever-temperature block thereof is within a predetermined temperature range. Then, the fever-temperature block is analyzed to determine if it is corresponding to the skin portions of the visible light image data. Thereafter, if the result of the previous step is yes, then a warning signal is issued to indicate that the testee has fever.