The R.C. silo that has been constructed is analysed and summarized in the paper, and unbonded prestress concrete silo is put forward. A lateral pressure calculation for melation to the silo wall is given by studying on the state of medum in the silo, so that, the thickness of the silo wall and the prestress steel area can be estimated and calculated approximsely. Some impartant detail construction of silo is given in this paper.