Abstract: To simulate the plane strain thermo-mechanical effect of cylindrical shell radiated by X-ray, the problem about energy deposition calculation in irregular quadrilateral grids must be solved. In this paper, a strict integral method was adopted to calculate the energy deposition, and relatively accurate result was obtained. Then three convenient arithmetics were presented, by which three approximate numerical results were gotten. Comparing the approximate results with accurate result, the conclusions are obtained as follows: The midpoint integral and parallelogram approximation arithmetics both save computation time and have high precision, and they can replace the integral method to compute energy deposition very well; the midpoint integral arithmetic is of better applicability for it is not confined by the grid plot; the cosine approximation arithmetic generates too large error to be used in numerical simulation despite of saving more time.