Objective To analyze the characteristics of blood loss for laboratory test of critically ill premature infants,and to seek feasible measures to reduce the blood loss.Methods Two hundred and forty-six cases of critically ill premature infants admitted to the neonatal intensive care unit from April 2012 to April 2013 were analyzed the blood loss for test during the hospitalization and the clinical features of blood loss with different gestational age,different weight within the first four weeks after admission.Then the application of blood loss according to test category was described.The blood volume demanded in theory was determined by the formula B =5 (∑ s + 0.1),then calculated the phlebotomy overdraw on the basis of the practical blood loss and analyzed the characteristics of overdraw per patients per day in first two weeks after admission.Results Among 246 patients,The median blood loss figure was 25.57 ml for each infants with the range between 7.10 ml ～ 119.20 ml,and the blood loss concentrated in first four weeks,which showed a decreasing trend with time.There was a statistically significant difference(P ＜0.05)that the smaller gestational age,the lower birth weight,the more daily blood loss per patient per day in first two weeks,but no significant differences(P ＞ 0.05) between the third and fourth week.The largest proportion of the blood samples was used for clinical chemical tests(31.49％),followed by blood gas analysis (19.03％),immunoassays (12.69％),blood cultures (12.63％),hematology (12.28％).The practical blood loss was about twice times of blood volume demanded for tests in theory,which the median was 7.8 times to the latter(25.57 ml vs 3.26 ml).It showed statistically significant difference(P ＜0.05) between blood overdraw per patients per day in the first week and the second week.Compared with different gestational age and birth weight,the difference of overdraw was also statistically significant(P ＜0.05).According to test category,blood culture was the most significant samples of phlebotomy overdraw,followed by biochemical,other,blood gas analysis,the percentage was 76％,64％,45％ and 41％ respectively.Conclusion The blood loss for laboratory test and the phenomenon of blood waste is serious in critically ill preterm infants.The smaller the gestational age is,the lower the weight is,the amount of blood loss and phlebotomy overdraw are more significantly.Biochemical and blood gas analysis are the main items of blood loss.