Condition of water separated for fuel filters tested is different because of differences of water injection methods in the test of coarse droplet water separation efficiency with which results of water separation efficiency can be affected. At the same time test results also can be influenced because of the length of drain time interval. Influences of water injection method and drain time interval on results of water separation efficiency test for the same kind of fuel filters under the other same conditions in the test of coarse droplet water separation efficiency were mainly discussed.