In order to discuss the minimum eigenvalue of adjacency matrix in the class of complementary graphs of the tricyclic graph with a given order of n and n－4 pendent vertexes, the unique graph whose minimum eigenvalue reaches the minimum is characterized. Based on the simple undirected connected graph,the minimum eigenvalue of the graph is studied from the structure of the complement graph, and the minimum eigenvalue of the adjacency matrix in the complement graph class of the tricyclic graph with a given order of n and n－4 pendent vertexes reaches the minimum unique graph when the value is [WTBX]λ([WTHX]G[WTBX]([XC符号1.eps;%85%85;P](n-4)/2,(n-4)/2[XC符号2.eps;%90%90;P])^C)[WTBZ]. The result shows that the associative graph adjacency matrix is a matrix which represents the adjacency between vertices, and its minimum eigenvalue is the minimum eigenvalue of graph, which can describe the essential properties of graph well. The conclusion from this research shows that the minimum eigenvalue of the complement graph of the tricyclic graph with a given order of n and n－4 pendent vertexes reaches the minimum eigenvalue, which provides certain reference for further study of the minimum eigenvalue of the adjacency matrix in the complement graph class.