Using one kind of main mercury methylation iron reducing bacteria of Geobacter sulphurreducens PCA strains as targeting bacteria, two kinds of quinolones ciprofloxacin and ofloxacin were chosen to study the influence of antibiotics on PCA strains and its ability to methylate mercury in combined pollution. The experiment results showed that a promoting effect of antibiotics on growth PCA was found under the low concentration. Through the detection of the concentration of antibiotic and the figure of ESI scan, it was found that Geobacter sulphurreducens PCA could metabolize ofloxacin, but ciprofloxacin could not be degraded by Geobacter sulphurreducens PCA. Methylation of mercury was promoted by the presence of two kinds of antibiotics, the methyl-mercury conversion rate of ofloxacin to Geobacter sulphurreducens PCA was 4.21 times higher than that of the control group, ciprofloxacin was 2.27 times, and the addition of two mixed kinds of antibiotics was nearly 2 times respectively. In the mixed solution, there is no superimposed effect of methyl-mercury.