In order to solve the deliquesced fertilizer adheres to fertilizer conveying pipe, and leads to fertilizer conveying pipe blocked, a kind of fertilizer amount adjusting mechanism of deep-fertilization machinery for paddy field was designed. This adjusting mechanism was taken as research object, the distance between hinge axis and the center of blade connection seat, the distance between hinge axis and sliding limited post axis, the rotation angular velocity of cam ring and the angular velocity of blade rotating around hinge axis were taken as objective function, the diameter of fertilizer through-hole, the number of blades and the changing range of curvature radius of guide chute were taken as constraint conditions, the aided design and analysis software for fertilizer amount adjusting mechanism was programmed by VB software, through which kinematics optimization was carried out for fertilizer amount adjusting mechanism. The obtained optimal parameter ranges are: the radius of inner ring of cam is 30mm, the number of blade is 6, the distance between the hinge axis and the center of blade connection seat is 47.5mm, the distance between hinge axis and sliding limited post axis is 12.5mm, the rotation angular velocity of cam ring is 25-35r/min, the angular velocity of blade rotating around hinge axis is 30-35r/min. According to optimization results, the fertilizer amount adjusting mechanism was simulated by Pro/E software, the simulation results were validated by experiment. The results show that the adjustable range of diameter of fertilizer through-hole for fertilizer amount adjusting mechanism is 9-56mm, the sliding limited post of blade and the guiding chute of cam ring have good sliding performance, and the designed fertilizer amount adjusting mechanism can satisfy the expected design requirements.