Compared with ordinary azo dye pollutants, metal complex azo dyes are usually more recalcitrant and have more serious harm to our environment. This study focused on biodecolorization of acid blue 193 (AB 193), a typical metal complex azo dye, by Shewanella oneidnesis MR-1 (MR-1) under anaerobic conditions with neutral red (NR) as electron shuttle. The results indicated that effective biodecolorization of AB 193 by MR-1 was dependent on the presence of NR as electron shuttle. At presence of 1-5 μM NR, MR-1 could successfully decolorize AB 193, but hardly decolorized it without NR added. NR was found to be able to significantly improve decolorization capacity of MR-1 by accelerating electron transfer between dyes and cells. And the optimal biodecolorization parameters gotten by response surface methodology (RSM) were temperature 30.1ºC, pH 7.0, 52.7 mg/L of initial AB 193 concentration and 3.5 μM of NR dosage, respectively to achieve maximum AB 193 decolorization (95.98%) after 144 h. Furthermore, the phytotoxicity of AB 193 to rice was significantly reduced during the decolorization process.