A feasible and fully automatic ramie decorticator was designed in the transverse-clamping delivery using the characteristics of ramie fiber decorticating, further to alleviate the ramie fiber stripping with high labor intesity. The decorticator implemented the fiber decorticating for the base and top of the ramie stalk in sequence. The flexible clamping and conveying of ramie stalk and fiber were adopted to ensure the clamping force without damaging the fiber. Without changing the conveying direction of ramie stalks, the whole ramie stalk fiber was stripped, indicating that the small size of machine was used to realize the fully automatic fiber decorticating of ramie. 5 steps were completed in a decorticator, including stalk feeding and conveying, base fiber decorticating, changing clamping, top fiber stripping, and fiber output once for all. The key components included the clamping and conveying device, the fiber decorticating device, and the end-change clamping device. The optimal ranges of key parameters were determined on the quality of ramie decorticating. Taking the decorticating clearance, drum and conveying speed as the influencing factors, mathematical models were developed for the fiber percentage of fresh stem and the impurity rate of ramie fiber. A combination of optimal parameters was achieved to clarify the influence of operating parameters on the ramie fiber decorticating. A multi-objective optimization was carried out in the Box-Behnken test. The results indicated that: There was a significant effect of decorticating clearance, drum speed and conveying speed on the fiber content of fresh stems and the impurity rate of raw fiber. The model interaction of decorticating clearance and drum speed also posed a great impact on the fiber content of fresh stems and the impurity rate of raw fiber. Moreover, there were obvious coupling effects of experimental factors on the fiber content of fresh stem and the impurity rate, but not a simple linear relationship. In the multi-objective parameter optimization, the optimal parameters were determined for ramie fiber decorticating: the decorticating clearance of 4.0 mm, drum speed of 330 r/min, and conveying speed of 0.36 m/s. A validation test of ramie fiber decorticating was carried out under the optimized conditions. The results demonstrated that the fiber content of fresh stem was 5.04% and the impurity rate of raw fiber was 1.18%, where the relative errors of indicators and the model predictions were less than 5%, indicating a high accuracy of prediction model. The productivity of machine was up to 142 kg/h, beyond the design specifications. The gum content of raw fiber was 22.85%, and the bundle breaking tenacity of ramie was 4.56 CN/dtex, indicating that the fibers of decorticating machine were suitable for the national standards of second class ramie fiber. The finding can provide a theoretical basis and technical support for the fully automatic ramie decorticator.