To achieve effective operation of litchi mechanized bloom thinning, a novel flexible thinning mechanism was developed. By implementing the experimental studies on different treatment methods, it was concluded that the speed and spacing of plastic string both had a significant influence on the thinning time and the rate of thinning flower. No significant differences were found in terms of the fruit-set quantity, fruit mass and fruit size. The thinning time was inversely and positive proportional to the rotational speed of plastic string and space separately, while the flower thinning rate was positive and inversely proportional to the rotational speed of plastic string and space separately. With different mechanical thinning treatments, the fruit mass and fruit size significantly increased along with fruit size and fruit shape index were relatively consistent compared to the control, which the fruit size difference was large. The mean fruit mass and fruit set quantity per cluster had a negative correlation.