Aiming to address the common issues of low conveying success rate, high miss holding rate, high stem breakage rate, and poor reliability in the process of clamping and conveying garlic plants by garlic combine harvesters, a kind of variable stiffness flexible clamping conveying device for garlic was designed. The overall structure and working principle of the clamping conveying device were elaborated and analyzed. Taking different harvest periods (early stage, middle stage, late stage) of Lanling 46 cloves garlic, Jinxiang hybrid garlic, and Jinqi early maturing garlic varieties as research objects, physical property tests of garlic stems under different moisture contents were carried out. Through theoretical calculation and mechanical analysis, key components were optimized;the working process of clamping conveying was analyzed to determine the key factors affecting its performance. An EDEM-MFBD coupling simulation model of the clamping conveying device was established and simulated to explore the influence of different operating parameters on the stress of garlic stems. Taking the speed ratio of clamping conveying speed to forward speed, feeding angle, and elastic coefficient of floating wheel as test factors, and the conveying success rate, miss holding rate, and stem breakage rate as test indexes, a quadratic regression orthogonal rotation combination test was conducted. Regression models of each test index with test factors were established, and the optimal operating parameters of the clamping conveying device were determined. The test results showed that when the speed ratio of clamping conveying to forward speed was 2.31, the feeding angle was 6.2°, and the elastic coefficient of the floating wheel was 3.95N/mm, the working performance was the best. At this time, the conveying success rate was 97.21%, the miss holding rate was 1.06%, and the stem breakage rate was 1.73%. In order to verify the working performance of the optimized clamping conveying device, a bench test was carried out, and the test results were basically consistent with the predicted results of the regression model.