In this study, a microdialysis (MD) technique was combined with high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for continuous monitoring of the dynamic variations of arsenic species in a microbe-inoculated culture broth. After optimizing the analytical system, retrodialysis was applied to assess the probe recovery and analytical performance of the proposed method. The mean probe recoveries of four arsenic species were in the range from 57.0 to 81.8%. The limit of detection (LOD) for arsenic was in the range of 0.6–1.8 ng mL−1 and 0.032 μM for MDA, respectively. The accuracy was assessed by an addition/recovery test with a satisfactory value of 98.07–109.08% for arsenic species and 93.57–108.15% for MDA, respectively. To evaluate the practical applicability of this method, we monitored, continuously for 72 h, the dynamic variations of the concentrations of the four arsenic species in a standardized bacterial sample (ATCC 25922). After adding the arsenic species into the bacteria-inoculated broth, we found that the concentration of As3+ decreased over time, whereas As5+ increased in concentration. In addition, malondialdehyde (MDA) was also monitored to evaluate the effect of oxidative damage of the arsenic species on the studied microbial system. Our analyses revealed that the dynamic variations of the arsenic species and MDA could be observed continuously during the microbial growth period. This economical and eco-friendly method might also be helpful for monitoring the transformations of other metal species, oxidation processes, and the bioremediation ability of microbial systems.