Abstract: Flowers were labeled with cards on flower-blossom days of Gentiana straminea plants cultivated in Zhuoni county, Gannan prefecture, Gansu. The seed weight and germination in capsules of the plants were measured once every three days after flower-blossom. Filling dynamics and germination characteristics of the plant seeds were studied to provide a theoretical and technical basis for determining the best time to harvest seeds. The fresh weight increased and reached its maximum on the 34th day following blossom, and then rapidly decreased to a level near its dry weight. This fitted a Logistic equation with a rapid increase during 13-34 d after blossom and finished changing on the 60th day. The grain filling rate showed a ‘slow-fast-slow’ pattern with two slow times because of rain. The seeds dehydrated increasingly faster as filling duration increased and the water content decreased to the end of this process. The seed germination rate was highest 43 d after blossom and showed a relatively stable value with prolonged filling, except for rain and cloudy conditions. The germination quality indicators were significantly and positively related to the grain dry weight and the seed filling duration respectively, and were positively related to the seed dehydration rate but negatively related to the water content in the seeds. All the above revealed that the seed filling process was mostly affected by weather and seed maturity affected the germination quality. The best harvest time should be 52-55 d after blossom (early-middle September), during which time the water content in seeds should be about 10% and the plants showing non-dissilient capsules. The seeds should be picked by stages with cloth or nylon bags on sunny days.