An experiment was conducted in a dark room to clarify the evaluation method for suppressing discomfort glare for fixed low mounting height luminaires lighting system (LMHL) in road lighting. Experiments were performed by a method of adjustment that set the output of the glare source to acceptable discomfort and a method of constant stimuli using a deBoer rating. As an evaluation index of discomfort glare, vertical illuminance (E_vg) at a height of 1,2 m above the road at the boundary between the lane and shoulder was defined. Experimental results show that E_vg correlates with deBoer rating. Also, the E_vg (relative value) for suppressing the discomfort glare to an acceptable level for the observer's adaptation luminance and the acceptable E_vg (absolute value) at an adaptation luminance of 0,5 cd·m^-2 were obtained from the experiment. Using these, we propose to set the acceptable E_vg according to the condition of the average road luminance in the design of road lighting.