Abstract: To clarify the period and the cytological characteristics of pollen abortion in the anthor of male sterile plant segregated from dominant nuclear male sterile flax line,the conventional paraffin methods were applied to observed the comparative anatomy of the flower bud and pollen development,using fertile and sterile flower buds as materials.The results showed that there existed obvious differences in mophology and cytology of sterile and fertile flower buds and pollen development.In this paper,from the beginning of seperation of the tapetal and middle-level,the anthor abnormal development and pollen abortion was devided into four phases,including seperation between the tapetal and middle-level;stagnation of microspore development;adhesion between tapetal and microspores and its gradual disappearance;and shrivel of anthor with no pollen.