The invention relates to the technical field of sealing property tests, and discloses a method for detecting sealing property of plate parts. The method comprises the following steps: step S1, coating liquid soap on a to-be-detected plate part; S2, preparing a cylinder which is smooth on the bottom, placing the cylinder on the to-be-detected plate part, so as to form a sealing cavity between the cylinder and the to-be-detected plate part; S3, using a vacuum pump to vacuate the sealing cavity; S4, and observing whether the to-be-detected plate part has bubbles in real time, if bubbles occur, the sealing property of the part being poor, and if no bubbles occur, the sealing property of the part being good. The method uses the vacuum-pumping method to detect. In detection, the part is coated with the liquid soap, and the cylinder is placed on the to-be-detected plate part, and the vacuum pump is started, and then the sealing property of the part can be determined through observing whether bubbles occur on the to-be-detected plate part.