The invention relates to a preparation method for an oxygen doped gallium arsenide polycrystal film which can give out red lights. In the method, gallium arsenide, gallium oxide and indium oxide are used as materials; a gallium arsenide substrate is used as the growing carrier of the film; hydrochloric acid, absolute ethyl alcohol, oxyful and de-ionized water are used as the washing agents; argon is used as a supporting gas and a protective gas; sodium hypochlorite, sodium hydroxide, phosphoric acid and de-ionized water are used as waste gas recycling agents; the preparation is carried out in a tubular high temperature furnace; an L-shaped quartz boat is arranged in a high temperature section in a quartz tube; the powder of the materials is arranged at the left part of the L-shaped quartz boat; the gallium arsenide substrate is obliquely arranged at the right part; under the temperature of 800 minus or plus 5 DEG C and the atmosphere of argon, state conversion, vapor deposition and film growing are carried out on the powder of the materials to grow into the black oxygen doped gallium arsenide polycrystal film which is in a wave shape formed by connecting gluing particles and gives out red lights; poisonous gases are recycled in the preparation, thus not polluting the environment; the preparation method has the advantages of short technique flow, fast film shaping and high product purity which can achieve 99 percent.