Abstract: Polyploid breeding was an important breeding method of lily. Induction 2n gamete was an idea way to get triploid lily. In order to know when induce 2n pollen could be induced, the relations between flower buds length and pollen mother cells developmental stages were studied. In this way, a foundation for creating triploid lily could be set up. Using flower buds of Lilium longiflorum ’Leishan’ as materials, the meiosis processes of pollen mother cells were observed. The results indicated that there were some relations between flower buds length and pollen mother cells developmental stages. The pollen mother cells was at the vigorous development stage when the flower bud had 1.0--2.5 cm in length. Pollen mother cells from the same anther were almost synchronization. Chromosomes of pollen mother cells duplicated once and then divided twice. One pollen mother cells would generate four pollens. Because there was no cell plate forming in the telophase I, it belonged to successive cytokinesis. The best time for 2n pollen induction was that the length of flower buds was 1.5--2.0 cm.