Three-dimensional (3D) emission computerized tomography (ECT) is a si mple,efficient and accurate technology for 3D imaging and measuring of combustion field,in which the calculation accuracy of weight matrix determines the accuracy and quality of tomographic rec onstruction.In this paper,a weight matrix calculation algorithm based on ray tracing of high-densi ty subgrids is studied. The measured zone is divided into high-density subgrids,and ray tracing is per formed according to the camera imaging model to determine the weight factors of discrete grid with p rojection pixels. Numerical simulation and reconstruction experiment for combustion flame prove t hat the algorithm has high accuracy and computational efficiency.The research has important theor etical reference for the practical application of 3D ECT.