To investigate the feeding characteristics of Oxyrrhis marina, Cyanobium sp.and Pleurochrysis dentata were used as food algae to culture O.marina respectively.The feeding processes, feeding rules and the color changes of cluture media of O.marina on two marine microalgae were analysed by the combined methods of microscopic examination, macro-observation and microscopic counting.The results showed that the feeding method of O.marina on Cyanobium sp.was wrapping the trichome sections slowly into the longitudinal groove, while the whole cell of P.dentata was incorporated into the longitudinal groove at the same time.The feeding rates of O.marina on two marine microalgae were 100% after inoculated by O.marina for 6 h, respectively.In static culture of O.marina, the color of culture media appeared pale pink to pink, whereas shaking culture media were not found.With the decrease of the initial density of O.marina(the cell density in Cyanobium sp.culture medium is 0.8×10⁴, 2.4×10³ and 0.8×10³ cells/mL repectively), the time when the population of O.marina reached the stationary phase required longer, namely, 3, 4 and 6 d respectively in culture media of Cyanobium sp., and the time when the population of Cyanobium sp.were fed up by O.marina required longer too, namely, 5, 10 and 15 d respectively.Also, with the decrease of the initial density of O.marina(the cell density in P.dentata culture medium was 3.9×10³, 2.4×10³ and 1.7×10³ cells/mL repectively), the time when the population of O.marina reached the stationary phase required longer, namely, 4, 5 and 12 d respectively in culture media of P.dentata, and the time when the population of P.dentata were fed up by O.marina required longer too, namely, 6, 7 and 13 d respectively.The experiment results showed that the feeding processes of O.marina on Cyanobium sp.and P.dentata were different for their different sizes and types and the color changes of culture media were affected by culture modes.Also the feeding of O.marina was affected by the kind of food alage and the initial concentration ratio of food alage to O.marina.During 15 day's culture period, Cyanobium sp.populations and P.dentata populations evolved to O.marina populations.