Abstract: In order to realize the parallelization of LARED-R-1,a serial code for numerical simulation of two-dimensional radiation transport,a directed graph is used to accurately describe the data dependencies.A parallel pipeline flux sweeping algorithm is applied to parallelize the code efficiently.Moreover,a special technique of buffering short messages for less communications is presented to improve the parallel performance.For a typical model discretized by 3 800 cells,100 energy groups and 40 directions,tests on a parallel machine show that the parallel LARED-R-1 achieves parallel efficiency by 80% with 64 processors and by 53% with 128 processors,respectively.