In-situ and nonintrusive 3D temperature measurement is very important for combustion diagnosis and controlling of pollutants. The temperature reconstruction technique based on radiation inverse analysis has received intensive attention. In order to reduce the computation cost and take boundary temperature into consideration, a discrete method is presented for 3D temperature distribution determination for an absorbing, emitting and scattering combustion medium and its boundary by using the emission image measured by four CCD cameras. First the radiative source term is retrieved through the discrete transfer method. Then, the temperature is inferred from the blackbody intensity obtained by subtracting the media scattering and boundary reflecting contribution from the source term by the discrete ordinate approximation. The least squares minimum residual algorithm is improved to solve the ill-posed reconstruction equations. The performance of the proposed method is examined by numerical test. The effects of measurement noise and radiative properties on the reconstruction accuracy are investigated. The results show that the method proposed in this paper is capable of reproducing the temperature of the medium and its boundary accurately, even with noise. The reconstruction time cost is reduced significantly compared with those of other methods.