We present a high brightness LCD backlight unit (BLU) only with the optimal lamp assembly without additional prism sheets such as BEF, DBEF etc. Many factors like lamp position, lamp reflector shape and LGP greatly affect luminance and uniformity of backlight. In this paper, we pay much attention to lamp position and lamp reflector frame so as to find out how they affect BLU properties. With position and reflector shape alteration, the optimal lamp assembly BLU luminance can be 7.49% up compared with the standard according to simulation result. Moreover, there is lower white line in the output of the optimal design of BLU and the luminance uniformity is the same with the standard. At the same time, we study on how to decrease white line defect by means of lamp assembly alteration and have made progress. Lamp reflector shape alteration, LGP moving nearer to lamp are all beneficial to white line decrease.