The present status of research and application of rice seedling trays was introduced, and the operation performance of the industrialization automatic seedling nursing production line after deformation due to long-term use or improper transportation was detailed. Regarding deformation of hard tray like blanket as the research object, a deformation measurement technology was put forward. Three indexes of deformation, such as rupture length, twist warp and bending deformation, were introduced into the study. According to the above results, the deformable seedlings were divided into four grades, mild, moderate, slightly severe and severely deformed seedlings, and the applicable criterions of four kinds of deformation seedling plates were standardized. In order to verify the reasonableness and feasibility of the grading evaluation of the deformed seedling tray, from the point of improving the mechanical reliability of precision seeding seedling production line, deformation seedling tray was selected in maximum for seedling nursing production line. The success rate of tray feeding and tray stacking and the seed exposed rate as the evaluation index, 2SJB-500 precision rice sowing seedling nursing production lines were used to test various deformed seedling trays’ seedling nursing performance. The test proved the evaluation accuracy of the grading of deformed seedling tray and revealed the relationship between the deformation of the seedling tray, the index of the deformation amount and the productivity. For the four types of deformed tray, the success rate of tray feeding and the success rate of tray stacking showed an obviously declined trend, the seed exposure rate showed an increased trend with the increase of productivity. The tray with mild deformation and moderate deformation had small deformation, the tray of mild deformation can keep going on using;for moderate deformed tray, if the flange or the bottom of the tray existed a little broken, it should be properly removed on the operation, which can be used for the seedling nursing production line in lower productivity;for slightly severe deformed tray, if there was a larger deformation index, it should be selectively removed on the operation. As for the tray edge with many broken areas, the large bottom crack, the serious twist degree in some seedling trays, it can be directly removed;for the severe deformed seedling tray, it should be directly removed on the operation, otherwise it would affect the final seedling nursing performance in the factory production line. The proposed technology of the deformation measurement in tray was simple and easy-to-operate for evaluating the deformation degree of tray intuitively and vividly. Meanwhile, this guideline provided a research basic for the automatic identification, detection and elimination system of deformed seedling trays in the subsequent seedling production lines.