This study on the sectional and vertical distribution of dissolved oxygen (DO) and the O2 fluxes across the sea-air interface in East China Sea (ESC) waters shows that the waters were in steady state and that the difference of DO was great in upper and bottom waters in Apr. 1994; but that seawater mixing was strong and the difference of DO was small in upper and bottom waters in Oct. 1994. The above conclusions were specially obvious in continental shelf waters under 100 m. The DO maximum in subsurface layer waters appeared only at several stations and in general the DO in the waters decreased with depth. The horizontal distributions of O2 fluxes across the sea-air interface appeared in stripes in Leg 9404 when most regions covered were supersaturated with O2 seawater to air flux was large

and that on section No. 1 was 1.594 L/m2·d. The horizontal distribution of O2 fluxes across the sea-air interface appeared lumpy in Leg 9410

when most regions covered were unsaturated with O2·O2 was dissolved from air to seawater

and the fluxes were 0.819 L/m2·d on section No. 1 in Leg 9310

0.219 L/m2·d in Leg 9410. The main reasons for DO change in surface layer seawater were the mixture of upper and bottom layer water

and the exchange of O2 across the sea-air interface. The variation of DO by biological activity was only 20% of total change of DO.