Monte Carlo transport simulations of a full-core reactor with a high-fidelity structure have been made possible by mode-day computing capabilities.Performing transport-bumup calculations of a full-core model typically includes millions of buup areas requiring hundreds of gigabytes of memory for buup-related tallies.This paper presents the study of a parallel computing method for full-core Monte Carlo transport-buup calculations and the development of a thread-level data decomposition method.The proposed method decomposes tally accumulators into different threads and improves the parallel communication patte and memory access efficiency.A typical pressurized water reactor buup assembly along with the benchmark for evaluation and validation of reactor simulations model was used to test the proposed method.The result indicates that the method effectively reduces memory consumption and maintains high parallel efficiency.