Abstract: Generally speaking,the calculation to hidden-line problem for polyhedra is complexity.But the caluclation for 2.5D polyhedra is easier to tackle by taking advantage of the feature of the 2.5D polyhedra.In this paper the hidden line problem for 2.5D polyhedra is discussed and a fast algorithm is given.With this algorithm the depth testing is not needed and the works for solving for points of intersection become much less.