The study on loess collapsib ility has long ignored role of CaCO₃ W ith the a id of scann ing electron microscope(SEM) and X ray energy dispersivemicroanalys is(EDX or EDS),CaCO₃ distribution in loess was explored.Some indoor expermi en ts were carried out to smiulate loess collapse and study b eh aviors o f CaCO₃ in the process.Results show that bewt een loess particles exists plenty of CaCO₃,which is easily leached with irrigation water and lost in the process Its loss th rough movement is much greater than th rough leach ing,and increas ing with the percolation rate of irrigation water.Then CaCO₃ accumu lates in the subsoil layer.