Abstract: In order to prepare nano-selenium microfertilizer which is easy to absorb, nano-selenium was prepared by chemical reduction method. The morphology, size and stability of nano-selenium were studied by different drying treatments and scanning electron microscopy. The seed of Pisum sativum was mixed with nano-selenium, and then the pot experiment was carried out to determine the selenium absorption and selenium transformation rate of Pisum satirum seedlings. The results showed that under transmission electron microscope and scanning electron microscope, the nano-selenium prepared by freeze-drying was spherical particles with uniform distribution and size, and the average particle size was about 28 nm. When the seed dressing dose（nano-selenium/pea seed） was in the range of 0.25-2.50 mg·g^-1, nano-selenium microfertilizer has little effect on the physiological indexes of Pisum sativum seedlings. The selenium content in the root of pea seedlings reached a very significant level, and the selenium content in the aboveground part was significantly higher than that of the control and other treatments at the dosage of 2.00 and 2.50 mg·g^-1 seed dressing. In the range of 1.00-2.50 mg·g^-1, there was a significant difference in selenium absorption; In the range of 0.25-2.50 mg·g^-1, the selenium transformation rate decreased first and then increased. To sum up, the freeze-drying preparation method can obtain nano-selenium microfertilizer with uniform dispersion and size. When the seed dressing dose was controlled in the range of 0.25-2.50 mg·g^-1, the absorption rate of nano-selenium in the underground part of pea seedlings was greater than the selenium transformation rate, so nano-selenium microfertilizer can be prepared by freeze-drying method for Pisum sativum production.