Abstract: Objective　To investigate the effect of Glutamine (Gln) on the expression of PCNA in intestinal tissue of neonatal rats with necrotizing enterocolitis (NEC), and to explore the protective mechanism of Gln in intestinal mucosa. Methods  Forty-eight neonatal rats at the age of 48 hours were selected, and divided into 4 groups, control group, Gln group, NEC group, NECGln group. Each group had 12 rats. Control group were fed mice milk substitutes; Gln group were fed mice milk substitutes mixed with Gln; NEC group were fed mice milk substitutes and had cold/ hypoxia exposure twice a day for 3 days; NECGln group were exposed to cold stress, hypoxia and treated with Gln mixed in the milk. The expression of PCNA was detected using immunohistochemical method. Results Compared with control group were and Gln group, the general condition was worse, and the weight was decreased in NEC and NECGln group. The infiltrated inflammatory cells, congestion, edema, intrinsic layer separation were observed in intestinal mucosa in NEC and NECGln group. The intestinal villus was lost in severe in NEC and NECGln group. The PCNA index was 34.17±5.78, 34.42±5.38, 15.00±1.94, 30.67±3.14 in control, Gln, NEC and NECGln group respectively, with significant difference between each groups (H=24.32, P=0.000). The expression of PCNA in NEC group was lower than that in normal, Gln, and NECGln group (P<0.008). The expression of PCNA had no significant difference among normal, Gln, and NECGln group (P>0.008). Conclusions  The expression of PCNA in intestinal mucosa was decreased in NEC rats. Gln supplement could raise the expression of PCNA in intestinal mucosa of NEC rats, and accelerate the speed of intestinal mucosa repair.