A selective laser melting technology-based apparatus for preparing a gradient material, comprising a laser scanning array lens, and a powder storer, a powder mixer, a powder scraping plate, and a working platform that are provided in sequence from top to bottom; the powder storer is provided with two or more partitions; a bottom portion of the powder storer is provided with an outlet; the powder mixer is provided under the powder storer and is a horizontally provided rotational mixer; the powder scraping plate is disposed under the powder mixer; the working platform is provided under the powder scraping plate; the laser scanning array lens is provided on the working platform. The present invention further relates to a method for preparing a gradient material, comprising powder storing, powder scraping, powder mixing, powder laying, and printing. The method can guarantee the two-phase powder ratio in each layer of powder not change.