The energy conversion efficiency of solar radiation and subsidies energy on ponds ecosystem cultured mainly with common carp in the marshland of the Sanjiang Plain during 1988~1992 was analyzed. The results showed that during the growing season, the net phytoplankton production in energy was 56.534GJ/hm², 54.9 15GJ/hm² and 51.717GJ/hm² respectively in common carp ponds with net fish yields of 2500 kg/hm², 3500 kg/hmz and 5000 kg/hm². In the aforementioned ponds, corresponding with three net fish yields, productions in energy of zooplankton, zoobenthos and plankton were IB. 148 GJ/hm², 16.343 GJ/hm² and 12.966GJ/hm² of zooplankton, 0.105GJ/hm²t 0.090 Gj/hmm² and 0.096GJ/hm² of zoobenthos, 17.367 GJ/hm², 15.716 GJ/hm² and 14.290 GJ/hm² of plankton respectively, while the productions in energy were 437.67 GJ/hm², 413.26 GJ/hm² and 33-1.98 GJ/hm² of suspended detritus, 196.50 GJ/hm², 199.31 GJ/hm² and 191.42 GJ/hm² of deposition respectively.The annual input of solar radiation was 25670~26440 GJ/hm². The efficiency of converting solar radiation to gross primary productivity ranged from 0.204~0.308%, and of converting net phytoplankton production to net yield of silver carp and big-head 1.195~4.815%, which showed that the ecological efficiency of converting solar radiation to total net yield of fish was 0.067~0.123%. The primary productions of the experiment ponds in the Sanjiang Plain were lower than those of other kinds of fish culture pattern in the south, because the solar radiation converses less efficiently in the marshland area. The effective nitrogen was the main restrictive factor of primary productivity on peat ponds ecosystem cultured mainly with common carp. The conversion efficiencies of subsidies energy input and output in the ponds and their relations with pond conditions, fish yield, feed structures and the administration measures were further given. The results showed that the annual input of subsidies energy was 180~260G J/hm², the energy conversion efficiencies of total subsidies energy (bioenergy and industrial energy), total bioenergy (feed energy and fingerlings energy) and feed energy converted into net production of fish were 8.91~14.05%, 10.96~1 7.20% and 11.06~17.57% respectively. The fish productivity, feed conversion efficiency and feed protein conversion efficiency were 1.795~3.807 M J/hm², 30.03~46.09% and 15.01~27.80%, The energy conversion efficiency of the ponds was 14.5%. The optimum fish production for the ponds cultured mainly with common carp was 5760 kg/hm², with a corresponding fish productivity of 3.807 MJ/hm², feed conversion efficiency of 46.09% and feed protein conversion efficiency of 27.80%, which were higher than those of other kinds of fish culture pattern. The energy cost (equal to the input energy divided by the fish yield) was 47.95GJ per ton fish, which was also lower than that of other kinds of fish culture pattern. Considering three different net production levels of 2500 kg/hm², 3500kg/hm² and 5000kg/hm², the net production of 5000kg/hm² is an optimal one. In the process of total energy flow of fish production, the solar energy accounted for a mere 17.8%, while the subsides energy for 82.2%.