In this paper, based on the analy si s o f the cha racteristics in redesig ning an existing railw ay line, research on the curv e-surface model fo r rai lwa y line is put forw ard. According to the fea tures o f terrain data di st ribution in reco nst ructio n desig n, this paper set up a combined fi sh-bone triang le net fo r the descriptio n o f the fo rmatio n and terrain o f both sides. In this paper, characteri stics and dist ributio n of surface da ta and computa tion defined on these curv e-surfaces are di scussed in detail.