In this paper, we consider the nonconvex quadratically constrained quadratic programming (QCQP) with one quadratic constraint. By employing the conjugate gradient method, an efficient algorithm is proposed to solve QCQP that exploits the sparsity of the involved matrices and solves the problem via solving a sequence of positive definite system of linear equations after identifying suitable generalized eigenvalues. Some numerical experiments are given to show the effectiveness of the proposed method and to compare it with some recent algorithms in the literature.We consider the following quadratically constrained quadratic programming (QCQP)where A, B ∈ R n×n are symmetric matrices with no definiteness assumed, a, b ∈ R n and β ∈ R. When B = I, b = 0 and β < 0, QCQP reduces to the classical trustregion subproblem (TRS), which arises in regularization or trust-region methods for unconstrained optimization [5,24]. Despite being nonconvex, numerous efficient algorithms have been developed to solve TRS [1,6,8,9,18]. The existing algorithms for TRS can be classified into two categories; approximate methods and accurate methods. The Steihaug-Toint algorithm is a well-known approximate method that