A tournament is a directed graph (digraph) obtained by assigning a direction for each edge in an undirected complete graph. There is a close relationship between domination graph and competition graph of tournaments. The exploration of domination graphs has played an important role in biology research of species competition graph. Given a tournament T with c vertices and tournaments S_i, i=1,2,…,c. Let D=T[S₁,S₂,…,S_c] denote the combined tournament of T. In this paper, we focus on the properties and structure of domination graph of combined tournaments. Based on current results, we present an efficient algorithm for the domination graph of a combined tournament.