Abstract: In order to study the sexual reproduction of endangered plant Gymnocarpos przewalskii, we measured its seed setting percentage, seed size, thousand seed mass, and the respondence of seed germination to light, temperature and PEG stress, and investigated the ecological adaptability of the species during seed germinating. The results showed that its seed setting percentage was 6.37%, length (2.03 ± 0.01) mm, width (1.37 ± 0.01) mm, and thousand seed mass 1.68 g. It was low requirement for light and temperature in the progress of seed germinating. The seeds germinated quickly and the mean germination time was less than 2 days in optimal temperatures. Water was a crucial factor to limit its seed germination, the osmotic pressure of -0.6 MPa was a critical turning point during seed germinating. The germination performance obviously dropped when the osmotic pressure was below -0.6 MPa. These seeds that didn′t germinate under draught stress went in to smart sleep and they germinated quickly when the draught stress was removed. All above showed the seeds of G.przewalskii have formed a good mechanism of utilizing limited water to achieve sexual reproduction quickly and effectively.