Abstract: Cards were hung as a flower sign in triennium Rheum palmatum plants cultivated in Li county of Gansu during blossom. The 1 000-grain weight, water content and seed germination in the plants were measured in period time after 10 d following the blossom day. Filling dynamic and germination characteristics of R. palmatum seeds were studied in order to provide theoretic basis for its seed standard production. The results showed that the 1 000-grain fresh weight increased and got at the highest value on the 36th day following blossom, and then rapidly decreased to the level near its dry weight, which fitted to Logistic equation with a rapid increase during 13-36 d after blossom. The grain filling rate showed ‘fast-slow-fast-slow’ pattern and went to bottom two times because of raining. The grains dehydrated grown fast with filling duration prolong and the water content decreased to the end. The seed germination vigor, germination rate and germination index were significantly improved with filling duration prolong within 36 d after blossom but showed difference further long, which were positively and significantly related with grain dry weight while negatively and significantly related with water concentration. All above revealed that the seed filling is affected by weather. The fast dehydrating rate in seeds is an important indication for seed maturation and the maturity affects its seed germination quality. The best harvest time should be during 46-52 d following blossom (at the beginning of July) during which the water content in the seeds should be 12%-16% with still non-perishing stems.