The pyrolysis behavior of nickel-calcium-loaded Loy Yang brown coals was studied. Two peaks of CO evolution appeared from nickel-calcium-loaded Loy Yang brown coal (Ni loadings: 4-7 wt %), one at 695 K and the other at 920 K, compared with those at 670-690 K and at 920 K from nickel-loaded coals. The amounts of CO evolved at 695 K were increased by adding calcium species to nickel-loaded Loy Yang coals. The calcium loadings did not affect the temperature and amount of CO evolution. EXAFS analysis showed that nickel metal particles were formed at 695 K in the nickel-calcium-loaded Loy Yang brown coals, while they were formed at 670-690 K in the nickel-loaded coals. The catalysis behavior of nickel species in the nickel-calcium-loaded Loy Yang coals is explained by the aggregation behavior of nickel species.