Abstract: Three kinds of union double jersey fabrics were produced with new polyester filament coolmax and their inner and outer layers were made with different single fiber fineness.Their dynamic moisture transfer properties were measured by using the Moisture Management Tester(MMT).The tester can calculate and compare the moisture transfer between the two sides of the fabric according to the moisture content which varies with time and obtain information such as moisture transport direction(from inner to layer) and rate etc.,therefore the one-way transport ability can be gauged.The experiments reveal that double jersey fabrics using different fiber fineness on the two sides has good one-way moisture transport ability,and the greater the difference of fiber fineness between the two sides,the more significant the transport speed and ability.