Because of the high water content of the household garbage, it is difficult to compost it. Therefore, this study was conducted to investigate the possibility of using coal fly ash as humidity conditioner for the household garbage composting. The summarized results are as follows : 1. The maximum temperatures were $35^{circ}C$ in spring, $47^{circ}C$ in summer, and $43^{circ}C$ in winter during the composting periods. 2. The mass was reduced to 70.5% after 60 days. The average volume reduced down to 74.7% after 60 days. 3. The seasonal variation of pH values showed a similar tendency and reached 8.5 after 60 days. 4. The water content was reduced at an early stage of composting and not much changed thereafter. It had 49.7% in spring, 33.9% in summer, and 56.5% in winter after 60 days. Ash contents were not much changed during the composting periods. 5. The contents of inorganic compounds were in the range of $0.06{sim}4.03%$ $P_2O_5$, $0.01{sim}2.87%$ CaO, $0.18{sim}1.43%$ MgO, and $0.39{sim}2.03%$ $K_2O$. Heavy metal contents were in the range of $ND{sim}14.08$ Hg ${mu}g/kg$, $ND{sim}0.80$ Cd mg/kg, $4.99{sim}28.95$ Cu mg/kg, $ND{sim}242.62$ Cr mg/kg, $ND{sim}20.24$ Pb mg/kg, and $ND{sim}59.87$ Zn mg/kg.