Abstract: To apply frequency spectrum analysis method,which is commonly used in signal processing and on digital geometry processing,it is necessary to choose a proper orthogonal function system.This paper first presents the detailed mathematic expressions of orthogonal V-system of degree 2 over triangulated domains,and then proposes a frequency spectrum analysis method to surface models,which is a direct application of the new constructed system.The method is to expand a surface model represented by piecewise polynomial of degree 2 in two variables in a V-series and then get the frequency spectrums,with which the surface model can be precisely reconstructed.Therefore orthogonal decomposition and reconstruction of a geometry object can be realized.Compared with the previous research,the expression of geometry information with the V-system of degree 2 has advantage of significant reduction in the quantity of data involved.The experimental results show that the proposed method is practical and feasible.