Introduction NEC is a worldwide problem in preterm very low birth weight (VLBW) infants with highly variable incidence affecting 2.6% to 28% of these infants; 1.2.Recent reports suggest increasing occurrence of NEC, estimating up to 9000 cases of NEC in the United States every year, with death occurring in 20 % to 40% of affected individuals. [1.3] As the number of very low-birth-weight infants increases, NEC remains a critical eminent problem. 3[4] The pathogenesis of NEC is unknown, but is widely considered as a multi-factorial disease; prematurity, enteral feeding, intestinal hypoxia-ischemia, and bacterial colonization are considered major risk factors. [4] Researches showed that proinflammatory cytokines, such as interleukin-1.6.8. (IL-1, IL-6, IL-8) and tumor necrosis factor- (TNF- ) 5-711-13 and anti-inflammatory cytokines such as IL-10 and transforming growth factor- (TGF- ) 8-1014-16 by intestinal epithelial cells is highly relevant to be involved in the final common pathway of pathogen of NEC.5-10 11-16.In mature bowel, the intestinal environment is capable of producing an array of cytokines important in the development and control of inflammatory responses11 8. In contrast, the immaturity of the neonatal intestinal immune system is evidenced by decreased numbers of immune cells 12.13 9.10. Recently, it has bee thought that inappropriate, accentuated inflammatory response to colonizing pathogenic flora at premature gut plays a major role, the inflammatory cascade further promotes spread of bacteria or toxin, and end up with ischemia, necrosis and even perforation. 14-1617.18.19 We and Bin-Nun had proved that probitics reduces the incidence and severity of necrotizing enterocolitis in preterm VLBW infants. 17.18 Nevertheless, there is no solid data in the literature as to the optima strains, timing, dosage and duration of probiotics administering to preterm VLBW infants at preset; and these need further investigate.