The block graphs are good models in many real-world applications, such as molecular graph model for Polymers and windmill networks. A block graph is a graph in which every block is a complete graph. In this paper, we first prove that, the entries of distance matrix D G ð Þ of block graph G satisfy the famous Four point condition (4PC) and we define an matrixWe find that, if the block graph is a tree or each of its blocks is a triangle, thenand it is independent of the structure of block graphs G. Finally, we obtain the ℳ G index, Wiener index W G ð Þ and Wiener polarity index W B G ð Þ of isomers of heptane, respectively.