Abstract: Cards were hung as a flower sign during blossom in lustrum Fritillaria przewalskii plants cultivated in Gannan, Gansu. The grain fresh weight, dry weight and water content in capsules of the plants were measured in period time after 5 d following the day. The grain filling characteristics were studied in order to provide theoretic basis for its seed standard production. The results showed that the 1000-grain fresh weight increased and got at the highest value on the 66th day following blossom, and then rapidly decreased to the level near its dry weight, which fitted to Logistic equation with a rapid increase during 41－66 d after blossom and finished at the end of 97 d. The grain filling rate showed ‘fast-slow-fast-slow’ pattern and went to bottom one time because of raining. The grains dehydrated faster and faster with filling duration elongation and the water content decreased to the end. The fastest decreased time in water content means the finish time of the grain maximum filling. The seed dry weight were positively and significantly related with the grain dehydration rate and the filling duration while negatively and significantly related with water concentration. All above revealed that the seed filling is affected by weather. The fast dehydrating rate and the stability of dry weight in seeds are the important indicates for seed maturation. The best harvest time should be during 77-82 d following blossom (at the end of July or beginning of August), during which the water content in the seeds should be lower than 40% and the seed capsules are not dissilient with still non-perishing stems.