Abstract: A concept of weighted reliability index normalized by the total capacity called index of macroscopic reliability is introduced in this paper to evaluate reliability of broadband network comprehensively and objectively. This index combines communication capacity with link reliability parameter effectively. The key technique to achieve complete algebraic calculation of this index is finding out an algebraic algorithm which can calculate all routes among network nodes. This paper proposes a new algebraic calculation routing algorithm, by which n times transformation operations can get all routes between two nodes for network with n nodes. The complete algebraic calculation of network reliability index is researched base on this new routing algorithm, it is easy to program and convenient to calculate reliability index of telecommunication network with computer. This method overcomes the difficulties in calculating normalized reliability index weighted by total capacity and can be used in practice. The calculation procedure of the algorithm is shown through examples in details and its correctness is validated.