Abstract: Rapeseed is the most widely distributed and grown oil crop in China. At the same time, with the improvement of related biotechnology, the variety of rapeseed functions has become increasingly prominent. According to the agronomic requirements for rapeseed, with the delay of the sowing date, it is necessary to increase the sowing amount to make up for the decrease of the emergence rate. In addition, as the operation speed of the planter increasing, the rapeseed seeder seeding frequency is needed to increase to meet the seeding density. For small size seeds such as rapeseed, when the sowing frequency is higher than 30 Hz, it can be considered that a high-flux seeds flow. It is great significance to research a kind of high-flux and small size seeds flow detection device to realize the detection of seeds quantities and missing seeds during high-frequency sowing of rapeseed. Because the rapeseed has a small size (0.8-2.2 mm), the seed signal generated by the conventional large and medium size detection device is weak and difficult to be captured. On the other hand, the existence of blind spots in detection has reduced the detection accuracy. In the text, when the sowing frequency reaches 62 Hz, the detection accuracy of the seeds flow detection device based on thin piezoelectric film and the seeds flow detection device based on thin-surface laser silicon photocell developed by the research team in the early stage was less than 85%. The reason is that when a high-flux seeds flow is formed at a high sowing frequency, the high-flux seeds flow will collide and increase the probability of aliasing inside the detection device, resulting in an increased probability of multiple seeds passing through the sensing zone at the same time, and detection accuracy is reduced. Aiming at the problem of insufficient precision of high-flux seeds flow detection due to agronomic requirements during the sowing of rapeseed and the high seeding frequency caused by high speed sowing, a method for parallel detection of high-flux seeds flow into multiple low-flux seeds flow was proposed, then the high-flux small size seeds flow detection device based on a combination of a shunt mechanism and a thin surface laser silicon photocell was designed. Considering the uniformity and fast passage of the high-flux seeds flow, the shunt structure was designed. Discrete element simulation software EDEM and bench test were used to verify the seeding uniformity when the shunt tube tilt angles. When the inclination angle of the shunt structure was less than 5°, simulation and bench test results of the consistency of the displacement each shunt tube at different inclination angles did not exceed 5.19% and 8.58% respectively. Combining the thin face laser and the seeding area, determine the relationship between the thin face laser emitting module angle, the inner radius of upper seeds through tube, and the distance of the thin face laser to the silicon photocell, comprehensive device cost and volume optimization to get the best combination of three parameters. Bench test of high-flux small size seeds flow detection device showed that within the seeding frequency range of 61.68 Hz, the accuracy of rapeseed detection was not less than 96.1%. The field test results showed that the detection accuracy rate was not less than 95.7% when the field seeding frequency was not more than 62.23 Hz, and no blocking phenomenon occured during the test. Normal light in the field and machine vibration had no effects on the detection accuracy of the device.