The vertical and seasonal changes of primary productivity in eel ponds were reported in this paper. The gross oxygen production in water column in eel ponds ranged 3. 51- 7. 90 g O2/ m2..day and the peak appeared in July to August. The photosynthetic oxygen production one meter or less below the water surface accounted for over 90% of the total production. The average compensation depth was 65- 74cm. Among the total oxygen consumption, fish occupied 22. 4%, .. water respiration.. 71. 3%, and detritus 6. 4% respectively. The oxygen production by photosynthesis accounted 67. 7% of the oxygen resources of eel ponds, the rest was supplied by air- dissolved and water- f illing. The photosynthetic energy effciency reached 0. 38% - 0. 85% of solar radiation. The efficiency of converting phytoplankton production to the yield of big- head carp was 1. 05% - 2. 32% and the ecological eff iciency of converting solar radiation to f ish production was 0. 009%- 0. 010% .