Cloud computing economically enables customers with limited computational resources to outsource large-scale computations to the cloud. However, how to protect customers’ confidential data involved in the computations then becomes a major security concern. In this paper, the authors present a secure outsourcing mechanism for solving large-scale systems of Linear Equations (LE) in cloud. Because applying traditional approaches like Gaussian elimination or LU decomposition to such large-scale LEs would be prohibitively expensive, they build the secure LE outsourcing mechanism via a completely different approach – iterative method, which is much easier to implement in practice and only demands relatively simpler matrix-vector operations.