The invention provides a method and a device for sealing a sample. The method and the device are applied to weather resistance test of galvanized plates. The method includes the steps: acquiring the sizes of the sample and a test zone and shapes of the sample and the test zone; determining the size and the shape of a sample sealing component according to the sizes of the sample and a test zone andthe shapes of the sample and the test zone, and manufacturing the sample sealing component based on the size and the shape of the sample sealing component; pressing the sample sealing component on the sample, and sealing the sample. According to the method, the area of the test zone is determined without manpower, a non-test zone is shaded without manual operation, measuring deviation is avoided,and accuracy of a measuring result is improved, so that accuracy of a rating judgment result of product quality is ensured.