Abstract: To improve the accuracy of cut & fill earthwork volume calculation，triangulate irregular network（TIN）was adopted to build the design model and real model.　In the earthwork volume calculation by means of primary construction of TIN model，it was difficult to realize the calculation by computer as the model was complex at the division boundary between the cut and fill earthwork.To solve it，secondary TIN construction was conducted to simplify the calculation mode by solving vector triangle calculation so as to facilitate the automatic realization by computer.The method and specific procedure for cut & fill earthwork volume by twice construction of TIN and the mathematical models used in the calculation are described.

Key words: Digital elevation model（DEM), TIN, Calculation of cut &, fill earthwork volume