In solving the problem on the mechanized harvest of tumorous stem mustard in the southwest hills area and understanding the tumorous stem mustard biological characteristics and agronomic requirements, a small tumorous stem mustard harvester with flexible gripping function was developed. The structure and working principle of the whole machine were described and analyzed, also the parameters of the core parts of the machine were analyzed and determined theoretically, which got the adjustment clearance of the flexible gripping device was between 60mm and 150mm, the speed of the gripping conveyor belt was 0.37m/s, the maximum gripping force required was 38.04N. The terrain imitation capability and structural dynamic characteristics of the cutting bench were analyzed, the results showed that the allowed topographic relief was 50mm, the maximum amplitude was at the position of the mounting cutter, and the first fifth natural frequency was 115.63~783.60Hz which was much higher than the excitation frequency of the engine and the terrain, so there was no resonance effect. The field test results showed that the cutting and gripping conveying mechanism had stable operation which was with small vibration, powerful cutting and moderate gripping force. The success rate of cutting was 89.5%, the damage rate of tumorous stem mustard was 10.8%, and the actual working efficiency was 0.035hm2/h, which basically met the requirements of the design and agronomic techniques. The research achievement would provide an important reference for the mechanization of mustard industry. 