In order to improve the success rate of conveying and reduce the damage rate of bulb, a floating clamping and conveying device was designed. According to the operation requirements of garlic combine harvester, multiple floating wheels were staggered in the working area and the chain tightness were adjustable, which met the needs of stable clamping. The rheological digital model of garlic stem was established, and the relationship between the key operation parameters on the clamping force of conveying device, conveying loss and bulb damage was analyzed. Taking the elastic coefficient of floating wheel, chain conveying speed and floating wheel spacing as test factors and the success rate and damage rate as test indicators, the test data were analyzed by Design-Expert software and the 3D response surface diagram was generated. The text results showed that when the elastic coefficient of floating wheel, chain conveying speed and floating wheel spacing were 2N/mm, 520mm/s and 83mm, the performance of the device was the best, and the success rate and damage rate were 97.42% and 1.36%. The optimization results were verified by tests, and the verification results were basically consistent with the optimization results. The research results could provide a technical reference for further exploring the technology of garlic combine harvester and floating clamping conveyor.