The invention relates to an automatic double-trunk clamping device and a method for a self-propelled vibration harvest machine, which mainly relate to the technical field of mechanical vibration harvesting of fruits. The device is formed by a walking mechanism, a rotary shaft, a vibration generator, a rear clamping rod, a rear pressure sensor, two middle pressure sensors, two middle clamping rods,a middle clamping rod, a middle pressure sensor, a front pressure sensor and a front clamping rod. The four clamping rods are arranged on the vibration generator, the pressure sensors are arranged onthe clamping rods, and the vibration generator is arranged on one side of the walking mechanism through the rotary shaft. The automatic double-trunk clamping device and the method are simple in structure, easy to control and reliable in performance; fruit tree trunks are mechanically vibrated, so that the labor intensity is low, and most of mature fruits are fallen off; with the mechanism, the personnel risks of orchard workers caused by climbing trees are avoided, and the mechanical requirement on continuous walking type operation is met; the four clamping rods can realize the harvesting offruits of two fruit trees at the same time, and the work efficiency is greatly improved.