In the process of stabilized fly ash co-landfilled with municipal solid waste (MSW), the leaching risk of heavy metal from stabilized fly ash by landfill leachate might exist. Based on batch leaching experiments, the research investigated the leaching behavior of heavy metals (Cd, Cu, Zn, Pb, Cr, Ni) in chelating agent-stabilized fly ash and phosphoric acid-stabilized fly ash with various liquid to solid (L/S) ratios (10:1, 20:1, 30:1, 50:1, 100:1, 150:1, 200:1) by using fresh and matured leachate as extracting agent. The results showed that the leaching trends of Cd, Cu and Zn were similar, which increased at first and then decreased with the increase of L/S ratio; and their respective maximum leaching concentrations were occurred at the same L/S ratio of 20:1. The leaching concentration of Pb increased slowly with the increase of L/S ratio. The change trend in the leaching of Cr and Ni varied little, indicating that the impact of L/S ratio on the leaching of Cr and Ni was not significant. Cd and Cu were more easily leaching out with fresh leachate compared with matured leachate; however, there was no significant difference in the leaching concentration of Zn, Pb, Cr, and Ni with fresh or matured leachate. Overall, the chelating agent-stabilized fly ash showed a better stability than the phosphoric acid (H₃PO₄)-stabilized fly ash when leached with fresh and matured leachate.