A method for testing a quality of powder spreading, comprising the following steps: S1: illuminating, after a powder spreading apparatus completes spreading of a single layer of powder, a forming area successively and separately by light sources symmetrically disposed on two sides of the forming area perpendicular to a powder spreading direction, and photographing, by a photographing apparatus located above the forming area, a powder spreading surface separately illuminated by each of the light sources on two sides, to obtain two images of powder spreading with different lights sources; S2: synthesizing the two images of powder spreading obtained in S1 to obtain a synthesized image of the powder spreading surface; S3: determining gray scale values of points of the synthesized image, and if the gray scale values of the points are all the same, the powder spreading being successful, and if not, turning to S4; S4: processing the synthesized image by using a method of gray scale threshold segmentation to obtain a gray scale threshold of the synthesized image, extracting a contour boundary inside the synthesized image, and marking an area contained in the contour boundary as a suspected defect area; if the suspected defect area includes an area of which a gray scale value is greater than the gray scale threshold, the powder spreading fails; and if the suspected defect area is a highlighted area, its gray scale value is smaller than the gray scale threshold, the powder spreading is successful; determining, after the powder spreading fails, a cause of failure of the powder spreading according to distribution of the suspected defect area; wherein if the suspected defect area is a continuous line shape or strip shape, the failure of the powder spreading is caused by a scraper; or wherein if the suspected defect area contains a plurality of dispersed areas, it is first determined whether the failure of the powder spreading is caused by an abnormality of a powder supply system. S1: illuminating, after a powder spreading apparatus completes spreading of a single layer of powder, a forming area successively and separately by light sources symmetrically disposed on two sides of the forming area perpendicular to a powder spreading direction, and photographing, by a photographing apparatus located above the forming area, a powder spreading surface separately illuminated by each of the light sources on two sides, to obtain two images of powder spreading with different lights sources; S2: synthesizing the two images of powder spreading obtained in S1 to obtain a synthesized image of the powder spreading surface; S3: determining gray scale values of points of the synthesized image, and if the gray scale values of the points are all the same, the powder spreading being successful, and if not, turning to S4; S4: processing the synthesized image by using a method of gray scale threshold segmentation to obtain a gray scale threshold of the synthesized image, extracting a contour boundary inside the synthesized image, and marking an area contained in the contour boundary as a suspected defect area; if the suspected defect area includes an area of which a gray scale value is greater than the gray scale threshold, the powder spreading fails; and if the suspected defect area is a highlighted area, its gray scale value is smaller than the gray scale threshold, the powder spreading is successful; determining, after the powder spreading fails, a cause of failure of the powder spreading according to distribution of the suspected defect area; wherein if the suspected defect area is a continuous line shape or strip shape, the failure of the powder spreading is caused by a scraper; or wherein if the suspected defect area contains a plurality of dispersed areas, it is first determined whether the failure of the powder spreading is caused by an abnormality of a powder supply system.