Abstract: Farm structure engineerings are basic facilities for agricultural industrialization developing. It is significant to confirm the reasonable design working life of farming facilities. It is a guidance for designing and building the farming facilities with more economy and efficient. It will accelerate the planting and animal breeding with industrializations and standardizations. Based on the natural properties together with society properties of farm structures engineerings. The all consumptions impacted on the working life of the farm structures are analized. Dealing with many ullages contributed on structure wearing. The paper put forwards some principles, indudings once time,natural properties, functional and economic principles. Three ways, which are considering all property, function and benefit way, single engineering way and economic working life way,respectively, fix out the farming facilities design working life.