To evaluate the potential antibiotic resistance capability of cultured human colonic microbiota as a whole system when residual antibiotics enter the human intestine, the combination of viable cell counting and denaturing gradient gel electrophoresis (DGGE) method was used to study effects of the enrofloxacin (ENR) residue on the microbial diversity, antibiotic resistance, and anti-colonization capability in a human chemostat model. The results indicated that the ENR enhanced the microbial antibiotic resistance to the ciprofloxacin (CI), and a dose-dependent effect was observed. When exposed to 1.25 mu g/mL ENR, the growth of the tested bacteria (e.g., total aerobic bacteria, total anaerobic bacteria, Lactobacillus, Enterococci, Escherichia coli, Bacteroides fragilis) received little change, while the microbial diversity in this group was totally changed; In 12.5- and 125-mu g/mL ENR group, the quantities and microbial diversity received a dramatic change compared to their no drug stage, while the addition of the cultured human colonic microbiota to the probiotic group did enhance the colonization resistance (CR) of the cultured microbiota to Candida albicans SC5314, indicating its potential beneficial effect on human intestinal healthy and anti-infection capability.