Abstract: Let G=（V（G）,E（G）） be an undirected graph with n vertices and m edges, its vertex set be V（G）=v₁,v₂,…,v_n, and the edge set be E（G）. The ISDD index of a graph G was defined as ■. In this paper, the relationship ISDD（G） with other indices was studied by using inequalities and graph invariants, and the new upper and lower bounds of the ISDD index of a graph were obtained, and it was proved that ISDD（G） and SDD（G） were linearly correlated under certain conditions.