Abstract: To explore the effect of effective accumulated temperature on the quality of seed from different positions on the Cistanche tubulosa inflorescence, the effective accumulated temperature of the development of capsule, size and germination of seed from different positions on the inflorescence were measured. The results indicated that it was different effective accumulated temperature of capsule from different positions on the inflorescence, the effective accumulated temperature of the middle capsule increased by 104 ℃ than that of the upper capsule, the ratio with the seed size bigger than 0.7mm and 0.5~0.7mm in the middle capsule was higher than that of the upper capsule, weight per thousand seeds and germination of the seed in middle capsule were higher than those of the seed in the basal and upper capsule. The difference of effective accumulated temperature of capsule development is one of the important factors causing the different quality of seed from different positions on the C. tubulosa inflorescence.