The neutron diffusion equation is usually solved in a symmetric region.For a non-rectangular symmetric region,the nonphysical singular problem arises when the c onventional method of deriving nodal solution is employed.In this paper,a new me thod based on both symmetries of the problem and an analytic representation of t he nodal flux distribution is presented.The method is effective for the solution of multigroup diffusion equation in the symmetric region,especially for the non -rectangular problem.It can be applied in 2-D or 3-D problems and its applicatio n in hexagonal geometry is introduced as an example.The only approximations used in deriving the method are the treatment of unknown functions.The efficiency of the proposed method is demonstrated by results of various 2-D and 3-D benchmark problems using the GTDIF-H code.