Aiming to the problem that picking hole mechanism of deep-fertilization liquid fertilizer applicator can not meet fertilizer-spraying needle inserted and pulled out of soil vertically all the time, according to the meshing characteristic of combining gears for oval noncircular with round gears. A new kind of picking hole mechanism was designed to achieve variable speed and vertical posture at picking hole. The meshing principle of oval gears were used, which controlled every moment change of angular velocity to achieve variable speed picking hole in the working period, the characteristic met specific requirement, which had horizontal velocity of fertilizerspraying needle trend to zero inserted and pulled out of soil, small hole mouth was achieved. To achieve small hole mouth and picking hole for vertical posture, the mathematics model of mechanism was established, with the rotational speed of picking hole mechanism of 120r/min, forward speed of 1.2m/s and depth of picking hole of 80mm as constraint conditions, structure parameters of mechanism were obtained, including half shaft distance of oval gear shaft of 39.9mm, eccentricity of 0.15, diameter of circular gear pitch curve of 68mm and length of fertilizerspraying needle of 140mm, and virtual experiment was verified by using the ADAMS software. The experiments of highspeed camera and picking hole were carried out, the trajectory shape of fertilizerspraying needle, curve of level absolute velocity and hole width were obtained when the forward speed was 1.2m/s, rotational speed of picking hole mechanism was 120r/min and depth of picking hole was 80mm, the reasons for the formation of such results were analyzed. Experiments results showed that fertilizer-spraying needle still guaranteed the target that had small hole mouth and picking hole for vertical posture.