Objective To understand the heel filter paper blood thyrotropin (TSH) level of preterm infants, and explore the appropriate screening time on preterm infants so that provide more exact diagnostic criteria to clinic. Methods A total of 4 606 specimens of preterm were seek out from more than one hundred specimens of neonatus borned in Beijing in 2011, and were divided into six groups according to different gestational age, screening time, birth weight, and established term infants group as control.TSH value was detected by DELFIA method, and distribution and the differences of TSH in preterm infants were analyzed between those groups by statistical software. Results The heel filter paper blood TSH level of preterm infants was lower than that of full-term infants as a whole, and very-low-birth-weight infants and extreme preterm infants in the exists obviously of individual differences, distribution was not balanced;The TSH level of preterm infants in delay screen over two weeks was declined, general preterm infants for overall balanced declined, extreme preterm infants and very-low-birth-weight infants in centered of level changed slightly, but department of percentileis was rise in terminal high value;The TSH cut-off of general preterm infants and full term infants were basically the same, but dropped significantly in extreme preterm infants and very-low-birth-weight infants, and also in delay screen over two weeks. Conclusion Establish TSH cut-off should consider different gestational age, birth weight and blood collection time of effect.