On the basis of analysis to existing literatures by which the thinking problems are studied using mathematic method and according to nerve foundation of thinking of human brain, several concepts such as thinking map and thinking route are proposed in this paper by imitating neuron (a kind of chemical substance) transition procedures (routes) during thinking of human brain as maps in discrete mathematics. Number of thinking routes is calculated by means of digraph adjacency matrix theory in graph theory. After comparison, the results basically satisfy the thinking routes in reality.