Let G be a simple graph with n vertices and m edges. be the complement graph of G
δ and Δ denote the minimum and maximum degree of the graph G respectively. λ 1(G) and λ 1() denote the spectral radius of the graph G and its complements graph . In this paper we proved that λ 1(G)+λ 1() satisfies following inequality ① λ 1(G)+λ 1()≤-1+2n(n-1)+1-4δ(n-1-Δ) ② If G and without isolated vertices