The invention discloses a method for preparing molybdate from waste materials containing molybdenum. The method comprises the following steps: firstly, adding a certain amount of water materials containing molybdenum into a certain weight of sulfuric acid solution, heating and stirring the solution and filtering the hot mixed solution to separate filter residues and a filtrate; adding the filter residues into a certain weight of ammonia, controlling the pH value of the solution to be between 8 and 10, heating and stirring the ammonia added with the filter residues and obtaining a solution, and subjecting the solution to acid precipitation, crystallization and drying to obtain the molybdate; adding hydrogen peroxide into the solution turns pale yellow, stirring the solution till the filtrate is completely oxidized, and adding magnesia into the solution to adjust pH to be more than 7.5 and generate yellowish-brown precipitations, and filtering the solution to separate sediments and liquid which is used for diluting sulphuric acid; adding a certain amount of the sediments into a certain weight of sulphuric acid solution, heating and stirring the solution till the reaction finishes, filtering the hot solution to separate filter residues from a solution; washing the filter residues ammonia to separate the molybdate; and subjecting the solution to innocent treatment for discharging.The method has the advantages of small equipment investment, simple process, small energy consumption, low production cost and no environment pollution.