To explore the interaction between antibiotic and As concomitant contamination in paddy soil, a microcosmic cultivation experiment was conducted on a paddy soil in Xiangtan City, Hunan Province. By simulating the process of flooding and drainage in paddy soil, the effect of oxytetracycline (OTC) on the redox conversion of Fe and As was investigated. Results indicated that OTC could promote the reduction of Fe minerals in flooding incubation period, and the contents of dissolved, exchangeable and adsorbed/weakly crystalline Fe in soil significantly increased. Therefore, more ·OH radicals were detected in drainage incubation period, which accelerated the oxidation of dissolved As(III). It was proposed that the complexation between OTC and Fe(III) induced electron transfer and promoted the reductive dissolution of Fe minerals. At the same time, the presence of OTC increased the relative abundance of dissimilatory Fe-reducing bacteria, which also promoted the reductive dissolution of Fe minerals. In addition, the relative abundance of sulfate reducing bacteria increased in the presence of OTC, thus the formation of arsenic sulfide increased accordingly, which would decrease the content of dissolved As in flooding period. In general, OTC promoted the reductive dissolution of Fe minerals in the flooding period, but reduced the dissolved As contents by enhancing the production of arsenic sulfide. In drainage period, the formation of ·OH induced the rapid oxidation of dissolved As (III). These processes could decrease the uptake and transport risks of As in rice.