A halophilic cell strain was isolated that efficiently degrades high molecular weight-polycyclic aromatic hydrocarbon (HMW-PAHs) contamination in saline environments. This strain, which can degrade phenanthrene, fluoranthene, pyrene and benzanthracene, was isolated from oil-polluted soil with pyrene as the sole carbon and energy source in a mineral salt medium (MSM) of 5% salinity. The strain was identified as Thalassospira based on morphological observations and an 16SrRNA sequence and named Thalassospira sp. strain TSL5-2. After 25 days' cultivation in 5% salinity culture solution, strain TSL5-2 degraded phenanthrene by 100%, pyrene by 53.5%, fluoranthene by 60% (initial concentration: 20mg/L) and benzanthracene by 18.1% (initial concentration: 8mg/L), but could not degrade benzopyrene. TSL5-2 had a wide salinity tolerance range (0.5%-19.5%), with an optimal salinity of 5%. Adding yeast powder and peptone (5mg/L) to the MSM both improved the degradation of phenanthrene by TSL5-2, with degradation rates of 60.1% with yeast and 82.1% with peptone at day 5, both higher than the control group (46.1%). Yeast powder did not effectively improve the degradation of pyrene and benzopyrene. Peptone inhibited the degradation of pyrene, while accelerating benzopyrene degradation, with a pyrene degradation rate of 17.5% and a benzopyrene (5mg/L) degradation rate of 38.2% at 25 days.