The goals of this research are to understand the NO_x emission in direct injected diesel engine with premixed hydrogen fuel. Hydrogen fuel was supplied into the test engine through the intake pipe. Amount of hydrogen-supplemented fuel was 70 percent basis heating value of the total fuel. The effects of exhaust gas recirculation(EGR) on NO_x emission were studied. The exhaust gas was recirculated to the intake manifold and the amount of exhaust gas was controlled by the valve. The major conclusions of this work include: (i) the tested engine was run without backfire under 70 percent hydrogen fuel supplemented (ii) the peak cylinder pressure was decreased with increase of EGR ratio due to the decrease of oxygen concentration in an intake pipe and (iii) NO_x emission was decreased by 77% with 30% EGR ratio. Therefore, it may be concluded that EGR is effective method to lower NO_x emission in hydrogen fueled diesel engine.