Abstract: Table grapes are high-value horticultural fruit plant in modern agriculture. Yet their postharvest packaging and grading remain labor-intensive, resulting in low efficiency, excessive costs, and fruit damage. Existing equipment, primarily for general fruits, cannot fully meet the specific requirements of table grapes, such as thin skin, soft pulp, berry drop, and double-bag packaging. In this study, a special double-bag packaging and grading machine was developed for table grapes. Feeding, double-bag packaging, bag closing, weighting, and grading were integrated to improve the postharvest efficiency and quality of table grapes. The whole machine was composed of a feeding device, a transparent bag and a paper bag packaging system, a bag-closing, a weighing and grading device, as well as a frame. In the feeding device, a single-cylinder driven symmetrical linkage structure was adopted with universal ball joints and flexible buffer sleeves. The stable opening and closing of the material gates were synchronously realized to reduce mechanical interference and jamming, leading to the accurate and non-damaged feeding of grape clusters into the packaging unit. The double-bag packaging realized the mechanical picking, opening, and covering of transparent inner bags and paper outer bags after the cooperative movement of vacuum suction cup groups and pneumatic cylinders. Corrugated vacuum suction cups were selected for their adaptability to flexible packaging materials. A linear arrangement was adopted to calculate adsorption force and layout size. Reliable grabbing and stable opening of bags were fully met the size requirements of grape clusters. The bag-closing device also simplified the gathering gripper into a crank-slider mechanism. The wire-tying machine was cooperated to effectively tighten the bag mouth for the firm and consistent sealing, thus improving the packaging and appearance quality. The weighing and grading device was equipped with an HX711 cantilever load cell and a synchronous belt slide mechanism. Real-time and high-precision quality detection was realized during conveying. Grape clusters were then transported to the grading positions, according to the preset quality grading standards. Conveying, weighting, and grading were integrated after optimization. In terms of control system, a distributed control architecture was adopted using STM32 microcontroller. Multiple microcontrollers were responsible for the different execution modules. The action timing of each component was coordinated via serial communication. The connection time of each process was optimized to improve the overall operation efficiency and stability of the control system, indicating better scalability for function expansion. A series of tests were conducted to verify the performance of a double-bag packaging and grading prototype machine for table grapes under indoor windless conditions. According to table grape quality grading standards, packaging qualification rate, grading accuracy, and average processing time were selected as evaluation indices. A total of 50 trials were finally repeated with full-process video recording. The results showed that the packaging qualification rate reached 92.00%, the grading accuracy was 94.00%, and the average processing time per grape cluster was 58.00 s. All performance indices met the technical and efficiency requirements of practical postharvest production. Feeding, double-bag packaging, bag closing, weighing, and grading were stably integrated to effectively reduce labor input and mechanical damage to the fruit, compared with the manual operation. The double-bag packaging and grading machine can effectively combine packaging and grading functions during table grape postharvest. The parameters can be adjusted, such as suction cup spacing and packaging size, particularly for the structural adaptability into the similar postharvest fruits and vegetables.