This trail was conducted to investigate the effects of probiotics E.faecium and Aureomycin on the development of cecal bacterial flora in broilers.One hundred and eighty newborn broilers were randomly divided into control,probiotics and antibiotics groups.The digesta in cecal were sampled sterilely and rapidly from the broilers at the age of 7,14,21,28,35 and 42 d respectively.RT-PCR was used to quantify the number of Escherichia coli and Lactobacilli.DGGE was used to estimated the changes of cecal bacterial flora.The results showed that addition of probiotics could reduce the number of E.coli at the age of 21 d and increase the number of Lactobacilli at the age of 42 d significantly (P＜0.05).The DGGE profiles showed that it's a transitional period from 7 d to 14 d,and a relatively stable period from 14 d to 42 d for the cecal bacterial flora.However,compared with the antibiotics,the addition of probiotics could help cecal bacterial flora to get through the transitional period more efficiently and keep more steady in the relatively stable period.