1,4-Naphthoquinone was prepared by oxidation of 1-naphthylamine with manganese ore powder as oxidant in sulfuric acid, which first reacted with 1-naphthylamine to form the related ammonium sulfate. The effects of reaction temperature, oxidation time, reactant molar ratio, types of acids, concentration of sulfuric acid on the product yield were investigated in detail. The optimal reaction conditions were as follow: 1-naphthylamine 1.8 g, n(1-naphthylamine) : n(MnO2) = 1:7, mass fraction 40% sulfuric acid 61 g, reaction temperature 80°C, reaction time 3 h. The yield of 1,4-naphthoquinone was above 59.8% in this condition. This new developed process has the advantages of convenient operation, easy separation of the product and short productive period.