Abstract: This paper reports a fungi, Ful-2, isolated from the ulcerous skin lesion of Micropterus salmoides culturing in net cage. Artifical infecting Micropterus salmoides fry were successful, Ful-2 was preliminarily identified as Fusarium fusarioides. Ful-2 grows very well in PH 2.57 to 9.86. It tolerates higher salinity and can survive in media.with 13% NaCl. The infecting hypaes can be found from the histopathological sections. The crude extract of Ful-2 corn culture at low temperature was negative when tested for 9 kinds of trichothecenes toxin. The extract was toxic to pea seed germination, to rabbit skin response, to three kinds of fry, indicating the presence of a toxin other than 9 kinds of trichothecenes toaln. Ful-2 is highly sensitive to malachite green, methylene blue and mercury chloride etc, but isn't to cupric sulphate, cupric chloride, sodium chloide, sodium bicarbonate etc.