Abstract: In order to strengthen the practicability of maximum probability principle,this paper gives out some es-sential conditions needed for applying the principle to practice and puts forward a calculating method ofincreasing functions in optimum constitution system. The optimum constitution of farmland ecosystem ofwheat production in Linyi county of Shanxi province is analyzed.It's proved that the calculating method isreasonable and achieves flood results.Kcy words ：maximum probability, calculating method, farmland ecosystem.

Key words: ecological migration, effects of migration, resettlement spot, resident perception, Wulingyuan Scenic Area.