For typical #P-hard problems on graphs, we have recently proposed an approach to solve those problems of moderate size rigorously by means of the binary decision diagram, BDD [12, 13]. This paper extends this approach to counting problems on linear matroids, graphic arrangements and partial orders, most of which are already known to be #P-hard, with using geometric properties. Efficient algorithms are provided to the following problems. ffl Computing the BDD representing all bases of a binary or ternary matroid in an output- size sensitive manner; by using this BDD, the Tutte polynomial of the matroid and the weight enumeration of an (n; k) linear code over GF(2) and GF(3) can be computed in time proportional to the size of the BDD. ffl Computing the Tutte polynomial of a linear matroid over the reals via the arrangement construction algorithm in computational geometry. ffl Computing the number of acyclic orientations of a graph, i.e., the number of cells in the corresponding graphic arrangement, and further the number of its lower-dimensional faces. ffl Computing the number of ideals in a partially ordered set, i.e., the number of some faces of the corresponding cone in the graphic arrangement