Abstract: The earthwork calculation is directly related to the cost estimate and the selection of the project，and it is an important link in the construction stage.  Three cases formula about the grid method of earthwork calculation is adopted in this paper，and the comparison and analysis are carried out in detail by means of the practical example.  Three cases formula meets the design principle of cut and fills balance and have been widely applied.  When the terrain without regular ground leveling，the results may he different if the formulas for calculation of earthwork grid method are different.  Suggestions to improve the precision are put forward by increasing elevation points and reducing the grid length，the earthwork calculation is easily achieved with the help of the main mapping software CASS.

Key words: grid method, earthwork calculation, cut and fill balance, field leveling, CASS software