A novel reactor design is proposed to overcome the effects of gas generation and multiphase flow from the NaBH4 hydrolysis reaction. With a stainless mesh set in the middle of horizontal pack-bed reactor to provide gas (Gas flow from the top of the reactor) and liquid (Liquid flow from the effluent of the reactor) channels respectively, the multi-phase flow problem is reduced. First, the mathematical model of the three-phase reactor is built. The design variables of the three-phase reactor are weight of catalyst, bulk density of catalyst and gas phase volume (Prevent the liquid mist flow out through the gas channel). In this work, two different operating modes, adiabatic and isothermal, of a continuous hydrogen generation system using the NaBH4 hydrolysis reaction are explored. The feed conditions are 1.02 ml/min, 25℃ and 15wt% of NaBH4. The simulation result shown that the weight of catalyst, bulk density of catalyst and gas phase volume are 17.5 g, 1.8 g/cm3 and 50 cm3 for 100% conversion of NaBH4 which can produce around 500 ml/min hydrogen flowrate. The result is quite fitted with our experiment. Finally, a water recycled structure is proposed to collect and recycle the produced water from the PEMFC and the hydrolysis reactor back to the feed stream. The theoretical hydrogen storage of NaBH4 can change from 4wt% to 10 wt%, when the reactor inlet concentration of NaBH4 keeps at 15 wt% for using water recycled structure.