The image reconstruction in diffuse optical tomography (DOT) is regarded as a large-scale nonlinear optimization problem,whose solution strategy is usually based on a Newton-like iteration algorithm involving the construction and inversion of the Jacobian matrix. It becomes intractable,when the scale of the inverse problem is large. To overcome this problem,algebraic reconstruction techniques (ART),an iterative solving method based on row action,is proposed to reduce the computational effort,but which will result in poor image quality. In this paper,conjugate gradient (CG) method is employed here,which requires only the computation of the objective function gradient to avoid calculating and storing the whole Jacobian matrix. Step length is determined by inexact line search method. The proposed methodology is validated by reconstructing the image of the slab phantom containing two deeply-located absorption and scattering contrasting cubes. Compared with ART,we find that the CG method performs better than ART at the image quality ,convergence and the speed of it.