Biological invasion of ballast water has been detected to be a great threat to marine ecosystem and human beings. However, so far less suitable method has been developed to obtain an effective, economic, safe, operational and clean onboard treatment method of ballast water. Hence porous ceramic filtration and UV radiation (PCF&UV) combination treatment is studied in the paper to propose a novel way to solve the problem. Targeted for the IMO convention, alga removal efficiencies and bacteria inactivation efficiencies were tested at different alga density and different flow rate. The results showed that 100% targeted alga can be removed and 100% marine bacteria can be inactivated at the appointed alga density. Optimal flow rate of 7m 3 /h is proposed for a 6L porous ceramic filter according to the results. The mechanism behind high removal efficiencies and inactivation efficiencies were researched as well.