Abstract: To address the problems of high labor intensity, low manual picking efficiency, and the lack of suitable mechanical harvesting equipment for chili pepper production in the hilly areas of Guizhou Province, a small horizontal spring-tooth drum picking device was designed according to the local planting pattern and the physical and mechanical characteristics of chili pepper plants at the harvesting stage. The device used rigid-flexible coupled spring teeth to separate chili pepper fruits from the plants through impact and combing actions, thereby improving the removal rate and reducing the damage rate. Field measurements showed that the average plant height, lowest fruiting height, and crown width were 595, 304, and 331 mm, respectively. Collision dynamics analysis was conducted for fruits at normal fruiting positions, and kinematic analysis was conducted for fruits at the lowermost fruiting position. Based on the theoretical analyses together with the structure and working principle of the spring-tooth drum picking device, drum speed, forward speed, drum diameter, spring-tooth spacing, and device ground clearance were selected as the factors for single-factor simulation experiments. A flexible discrete element model of the chili pepper plant was established using EDEM software to investigate the effects of these factors on removal rate and damage rate. The single-factor simulation results showed that the removal rate first increased and then decreased with increasing drum speed, whereas the damage rate generally increased, and a drum speed range of 190～230 r/min was selected. The suitable forward speed range was 1.75～2.25 km/h. Within the range of 760～840 mm, drum diameter had relatively little effect on removal rate and damage rate; therefore, the drum diameter was fixed at 800 mm in the subsequent optimization. When the spring-tooth spacing was too small, frequent contact between the spring teeth and the plants increased fruit impact and damage, whereas excessive spacing reduced the probability of effective contact; therefore, a spring-tooth spacing range of 35～45 mm was selected. The suitable range of device ground clearance was 40～120 mm. A four-factor, three-level Box-Behnken response surface simulation experiment was then conducted using drum speed, forward speed, spring-tooth spacing, and device ground clearance as the experimental factors, with removal rate and damage rate as the evaluation indices. Analysis of variance showed that the lack-of-fit terms of the regression models for removal rate and damage rate were not significant, with P values of 0.4121 and 0.5812, respectively, indicating that the established models adequately represented the relationships between the experimental factors and picking performance. Multi-objective optimization with the maximum removal rate and minimum damage rate as the objectives resulted in an optimal combination of a drum speed of 210.39 r/min, a forward speed of 1.96 km/h, a spring-tooth spacing of 40.95 mm, and a device ground clearance of 87.51 mm. Under these conditions, the predicted removal rate and damage rate were 91.20% and 3.07%, respectively. For field operation, the optimized parameters were rounded to a drum speed of 210 r/min, a forward speed of 2 km/h, a spring-tooth spacing of 41 mm, and a device ground clearance of 88 mm. Five repeated field tests were conducted in Zunyi, Guizhou Province. The average removal rate and damage rate were 92.05% and 3.22%, respectively, and the operating efficiency reached 0.163 hm²/h. The relative errors between the field results and model predictions were 1.04% for removal rate and 4.04% for damage rate, both of which were less than 5%, demonstrating the reliability of the regression models and the feasibility of the optimized parameter combination. The developed picking device achieved stable picking performance under the tested field conditions and can provide a technical reference for the design and parameter optimization of compact chili pepper harvesters for hilly areas.