In middle school mathematics, some teaching contents embody a teaching idea of "combination of numbers and graphs", especially in the geometry part of middle school mathematics. Therefore, in the actual process of teaching, teachers should combine numbers and graphs to guide students to learn and explore some practical mathematical problems with intuitive and vivid graphics. Graph theory is a branch of discrete mathematics, which takes graph as its research object. A graph in graph theory is a graph composed of some vertices and edges connecting two vertices. This graph is usually used to describe a specific relationship between certain things. In a graph, a vertex represents a thing, and edges are used to represent specific relationships between connected two vertices. In the history of graph theory, the emergence of graph theory has solved many mathematical problems, especially some seemingly simple problems that are difficult to solve with traditional mathematical methods. The method of graph theory is widely used in middle school mathematics, especially in middle school mathematics competitions. This paper discusses some applications of graph theory in middle school mathematics. We first introduces graph theory through two specific problems in life, and then explores some applications of Ramsey number problem, bipartite graph and matching problem of graph theory in middle school mathematics teaching.