Abstract: A high-efficiency production model(Model A),combination of paddy-lotus rotation with fish/crab rearing in paddy fields,was put forward in light of the local physical conditions,regional advantages and the current agricultural farming structure of Baodi,Tianjin,and its ecological effects were analyzed.With the aid of Ecopath software,comparison in sustainability and net output value of the complex model with four simple models,rearing fish in paddy(Model B),rearing crabs in paddy(Model C),rearing fish and crabs in paddy(Model D),and just planting rice in paddy(Model E),was performed.Results show that in terms of Finn′s index,the five models were in the order of A>B>C>D>E;in terms of sustainability,Model A was superior to the other four,and in terms of net productivity,B/E ratio,O/I ratio and stability,it was 2.63,4.25,2.03 and 3.56 times as much as Model E,respectively.Compared with other four models,Model A is very high in net output value and thus put forth as an optimal ecological farming model for extrapolation in North(China).