Abstract: A method of preparing a durable air-permeable mold having dimensional accuracy and without cracks clue to the segregation of the ingredients of the aggregate and without a surface irregularity, which comprises compounding 100 parts by weight of an aggregate obtained by compounding metal powders with metal oxide powders in a weight ratio of 5:95 to 30:70, the metal of said metal oxide powders being the same as that of the metal powders, 80% or more of said metal powders and said metal oxide powders having grain sizes of 300 .mu.m or less, with 10 to 35 by weight of an auxiliary hardening material that is softened and melted during the sintering process, and 10 to 25 by weight of a binder that contains an evaporable component, mixing them to form a slurry mixture, pouring it in a pattern mold to obtain a mold, drying the thus-obtained mold, and sintering the dried mold in an oxidative atmosphere at a temperature of 600.degree. to 1200.degree. C.