Abstract: Abstract: Most orchard gardens are distributed in the subtropical and tropic zone, and especially in mountainous and hilly region in China. With the development of science and technology and the increasing cost in labor, the mechanized operation for fruit collection is needed. Existing small fruit collecting devices have bulky and complex structure and need to be equipped with high-power drive, and strict requirement in the tree spacing. In order to adapt to the mechanization collection of small fruit and improve the mechanical collecting device, based on the existing fruit collection equipment at home and abroad, and considering deployable and foldable mechanisms of the equipment, a collecting device with flank deployable and foldable mechanism was introduced in this paper. This collection device mechanism can reduce the bulk in process of moving, adapt in line spacing of the fruit trees, have larger coverage area in unfolding state, and can adjust quickly and effectively in operation to improve collecting efficiency. The collecting device consisted of three parts: flank deployable and foldable mechanism (the core mechanism), lifting mechanism, and mobile clamping mechanism. The displacement and coordinate point G at the end of the flank deployable and foldable mechanism were calculated by transformation matrix. Then kinematics of the flank deployable and foldable mechanism was analyzed, and the main components of the mechanism were optimized using genetic algorithm (GA) operated in MATLAB. Rod AB, AD, PE were taken as the main optimization variables by comparing the influence of variable rod length on the displacement of point G and ∠EFG. Given the radius in folding and unfolding, the maximum displacement of point G during the unfolding process and the minimum dimension sum of the rods were taken as the optimization objectives. In order to obtain the more preferable rod dimension, the optimization range of the rods was expanded about ±50 mm. And the final optimization range and optimal solution of the main rods dimension were obtained based on the restrictions by iterative calculation at last. The optimal dimensions of the main components were lAB=277.88 mm，lAD=661.64 mm, lPE=306.58 mm. The obtained results were used to modify the 3D model of the flank deployable and foldable mechanism, and the 3D model of this mechanism was imported into the dynamic analysis software ADAMS. From such model, then the motion trajectory of the mechanism was simulated and the dynamic simulation results showed that the driving torque was 2.4 N·m. The motor type was determined based on the results achieved by simulation. Finally, a prototype of the flank deployable and foldable mechanism was manufactured and tested based on the optimal theoretical model, and the trajectory of point G was recorded by the Phantom v5.1 high-speed camera. Due to precision and errors of the prototype caused by machining and assembling and errors from camera shooting angle and image processing, there was a slight deviation between trajectory of experiment and virtual simulation, but they were basically consistent, which verified accuracy and reliability on the theoretical design of this collecting device. Experiment results of mechanical harvest using a small fruit collecting device with flank deployable and foldable mechanism demonstrated that this collection device had practical value and this research provides a reference for the improvement of the other collection mechanism.