In this study, we used the graphene oxide (GO) solution, in which the concentration was from 0.005 wt% to 0.500 wt%, to modify the flexible arrayed ruthenium dioxide (RuO2) chlorine ion sensor. It is found that the flexible arrayed RuO2/0.010 wt% GO chlorine ion sensor had the best sensitivity (44.445 mV/pCl) and the linearity was 0.971. The electrochemical impedance spectroscopy (EIS) and atomic force microscope (AFM) were utilized to explain the relationships among the electron transfer resistance, GO modified amount and sensitivity. After that, we used the flexible arrayed RuO2/0.010 wt% GO chlorine ion sensor and the microfluidic measurement system to investigate the dynamic sensing characteristics with different flow rates from 5 mu L/min to 40 mu L/min. According to the experimental results, the best sensitivity and linearity of flexible arrayed RuO2/0.010 wt% GO chlorine ion sensor were 66.673 mV/pCI and 0.992 at 30 mu L/min.