Abstract: 【Objective】 Understand the period of microspore abortion and the factors affecting microspore abortion in poplar varieties to provide the scientific basis for breeding new male sterile poplar varieties.【Method】This paper used the male sterile Poplulus×euramericana ‘Siyang-1' aged 16 years as study material. In spring 2016, the flower branches were collected with water training at room temperature. Then, we regularly sampled and fixed the material to make paraffin sections, and observe the cellular development of pollen grains under an Olympus-bx51 optical microscope. Moreover, we observed the morphology of abortive pollen grains under a Quanta 200 scanning electron microscope and compared it with that of the male fertile variety ‘Nanlin 3412.' 【Result】The microspore development of ‘Siyang-1' began to develop abnormality after the tetrad period. In the mononuclear microspore phase, only a few cells formed mononuclear microspores, which were in a highly vacuolated or disintegrated state. The volume of microspores was obviously increased, showing signs of abortion. At the mature stage of pollen grains, the microspores began to disintegrate and the microspores were aborted. Only a small number of cells developed into two-celled pollen grains bonded to the remaining tapetum, which accumulated and clung to the inner wall of the anthers. The anthers shrank and dried, and no pollen was scattered. At the same time, the pollen grain morphology of ‘Siyang-1' was observed with the Quanta 200 scanning electron microscope. It was found that the pollen grains were abnormal and deformed, which was different from that of the normal pollen grains.【Conclusion】The abortion of ‘Siyang-1' began in the mononuclear microspore stage, and disintegrated at the mature stage of pollen grains, resulting in microspore abortion. The main reason affecting the abortion of ‘Siyang-1' was the delayed degradation of tapetum cells, which influenced the supply of nutrients to microspore development, resulting in microspore abortion. In addition, the concentration of Ca²⁺ in the anther chamber and the distribution of Uribe in the anther wall may also affect the process of microspore development. This paper provides a new idea for the study of male sterility of poplars, which is beneficial in the production practice in the future.