Para-xylene (PX), as an important industrial chemical, has largely been transported by sea, which is followed by frequent PX leakage accidents at sea. Seawater contaminated by PX can be treated by bioremediation using microalgae, but there are a limited number of microalgal species that can be used to biodegrade PX. In this study, a novel Rhodomonas sp. JZB-2 (Cryptophyta) was isolated from Jiaozhou Bay (China), which could efficiently remove high concentrations of PX from seawater. The experimental result indicated that Rhodomonas sp. JZB-2 could completely biodegrade 30 mg/L of PX in 6 d. The growth inhibitory kinetics of this strain matched those of the Yano model, and it was calculated that 9.682 mg/L was the best concentration for degradation of PX by Rhodomonas sp. JZB-2. Besides, the biodegradation was the main PX removal mechanism. Therefore, Rhodomonas sp. JZB-2 is expected to be used in the bioremediation of marine environments polluted by PX.