For the existing proportional valve with the U-shaped throttling grooves of the main spool, the discharge area change gradient of the valve port is more severe and the flow gain is large in the small opening, resulting in poor micro-motion characteristics such as unstable start, slower response and low flow control accuracy of the proportional valve in the small opening. A throttling grooves with slope-diverge-shaped was proposed. The discharge area change gradient of U-shaped throttling grooves and slope-diverge-shaped throttling grooves were compared and analyzed by theoretical calculation and simulation methods, as well as the displacement characteristics, flow characteristics and valve port flow characteristics under different valve port openings. It can be seen from the simulation results that compared with the U-shaped throttling grooves, the response time of the slope-diverge-shaped throttling grooves was shortened by 0.04s when the opening of the valve port was 1mm. When the opening of the valve port was 2mm, the displacement response time was shortened by 0.07s. And when the slope-diverge-shaped throttling grooves valve was ported at the small opening, its steady-state hydraulic power was smaller, the flow state was more stable, and the flow loss was smaller. And the experimental results showed that the displacement response time of the spool of the slope-diverge-shaped throttling grooves was shortened by 0.08s, and the linearity of the flow response characteristic curve was better. Finally, through the comparative analysis of the simulation and experimental results, it can be seen that slope-diverge-shaped throttling grooves, the discharge area change gradient of the main valve core was smoothly in the small opening, and the flow gain was relatively stable, which improved the smoothness of valve start-up, speed of response and flow control accuracy. In summary, the slope-diverge-shaped throttling grooves realized the improvement of the micro-motion characteristics of the proportional valve.