A novel membrane-UV reactor has been developed for dissolved oxygen removal from water. The reactor was fabricated from an UV light surrounded by silicone rubber hollow fiber membranes. Water saturated with dissolved oxygen was fed into the hollow fiber lumen, while hydrogen gas used as a reducing agent was introduced into the reactor shell. The hollow fiber membrane served as a gas distributor for hydrogen to be distributed evenly and then dissolved in water to react with the dissolved oxygen under the UV irradiation. The dissolved oxygen is, thus, removed due to the chemical reaction between the two dissolved gases. A mathematical model has also been developed for the novel membrane reactor. The effects of membrane resistance, gas and water flow rates as well as gas pressures on the overall performances of the reactor for the DO removal were studied theoretically. Experimental data obtained at various operation conditions were compared with the theoretical results and kinetic parameters for the dissloved oxygen and hydrogen reaction were evaluated.