Three-dimensional (3D) emission computerized tomography (ECT) is a simple,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 reconstruction.In this paper,a weight matrix calculation algorithm based on ray tracing of high-density subgrids is studied.The measured zone is divided into high-density subgrids,and ray tracing is performed according to the camera imaging model to determine the weight factors of discrete grid with projection pixels.Numerical simulation and reconstruction experiment for combustion flame prove that the algorithm has high accuracy and computational efficiency.The research has important theoretical reference for the practical application of 3D ECT.