Abstract:In order to understanding the relationship between the endangered mechanism and the female reproductive development of Diplopanax stachyanthus Hand.-Mazz., the megasporogenesis and development of female gametophytes were observed by using the paraffin section method. The results showed that the pistil of D. stachyanthus was single carpel, ovary inferior with one locule and one ovule. The amphitropous ovule located on a short flake placenta with single integument and thick nucellus. The single sporogonium differentiated from epidermis of nucellus; the megaspore tetrad was linear. In mature embryo sac, two polar nucleis fused into secondary nucleus before fertilization, three antipodal cells were undeveloped and degraded. The abnormal development happened at 2-nucleate embryo sac stage, two nuclei division was uneven and the small nuclei degenerated and disappeared. Therefore, it was suggested that the abnormal development of D. stachyanthus female gametophyte was the main reason for low setting rate.