To identify the relationship between salicylate 5-hydroxylase activity and the degradation rate of phenanthrene by moderately halophilic Martelella sp. AD-3, and to investigate their enzymatic characteristics. The products resulted from degradation of salicylic acid using the crude enzyme produced by AD-3 was analyzed using HPLC analysis, and salicylate 5-hydroxylase activities at different conditions was calculated according to the change of NADH absorbance at 340 nm. The salicylate 5-hydroxylase activity was higher during log-phase and early stationary phase of AD-3, and the enzyme activity was in consistent with phenanthrene degradation rate. The enzyme production was induced by phenanthrene and salicylic acid. The highest enzyme activity, 132.8 nmol/(min x mg), from strain AD-3 was obtained under the phenanthrene concentration of 200 mg/L, 3% salinity and a pH of 9.0. The optimum conditions for degradation of salicylic acid using this enzyme were 30 degrees C , pH 7.5, and salinity 3%. The V(max) and K(m) for the enzyme were 200 nmol/(min x mg) and 8.7 micromol/L, respectively. The salicylate 5-hydroxylase was produced in the degradation of phenanthrene in AD-3. The enzyme activity was related to phenanthrene degradation rate.