In view of missing filling seeds and suction hole blocking in the seeding process of small grain vegetable seeds in the pneumatic seed metering device, an approach for synchronous detecting the missing filling seeds and suction hole blocking of small grain vegetable seeds was proposed. Using the external interrupt and timer interrupt resources of ARM embedded system, the detection system determined the rotation speed of planter plate with a rotary encoder and adjusted the time window and the theoretical pulse frequency in real time. Then, the detection system collected the output pulse of the laser sensor and obtained the actual pulse frequency. By calculating the theoretical pulse frequency and the actual pulse frequency, the rate of missing filling seeds and rate of suction hole blocking were measured synchronously and displayed on the touch screen. With a synchronous detection by high speed camera system, experimental research on pneumatic precision metering device was carried out with the detection system. The seeds of three kinds of vegetables, such as white radish, middle double 11 rape and Shanghai pakchoi, were selected as the research objects. The test factors were the speed of planter plate and vacuum degree of suction chamber, and the rate of missing filling seeds and rate of suction hole blocking were used as test indexes. Experimental results showed that the system can adjust the time window automatically according to the rotation speed of planter plate. The relative deviation of missing filling seeds rate was not more than 1.67%, and the relative deviation of suction hole blocking rate was not more than 0.95%. This detection approach effectively solved missing filling seeds and suction hole blocking synchronous detection of small grain vegetable seeds in real time and provided a basis for analyzing the cause of seed drain and seeding device improvement design.