Abstract : Mucus plays an important role in protecting fish against pathogen invasion, signaling events, regulating osmotic pressure and so on. As mucins are the important skeleton components of the mucus, the researches on fish mucins have catch wide attention. However, few studies have been reported on fish mucin gene characteristic and expression pattern. In this study, Megalobrama amblycephala Muc5b mRNA(3895 bp length) was cloned and its tissues expression was analyzed by qRT-PCR. The result showed that sequence of M. amblycephala Muc5b had high homology with other vertebrates, and its N-terminal of predicted amino acid sequence contained several non-PTS region domains: three VWD domains, three C8 domains and two TIL domains(Fig.2). Gene expression indicated that relatively higher expression of Muc5b in gills and skin, lower expression in brain, spleen, kidney, almost no expression in liver and intestine(Fig.4). In addition, variation of Muc5b expression was detected in gills and skin after catching stress. Muc5b expression was significantly reduced in the gills (t-test, P < 0.05) at 1h after catching-stress, and recovered to initial level at 24h; On the contrary, Muc5b expression was increased in the skin at 4h(t-test, P < 0.05), then recovered to the initial level(Fig.6). Thus, the Muc5b expression can be influenced by catching-stress.