The invention discloses a assembling tool of illuminating source component and its assembling process comprising illuminating source component mounted in mounting frame which comprises clintheriform cardinal plate and fixing flat structure outspreading from side of cardinal plate. Meanwhile, the invention also discloses a method for assembling the illuminating source components applying for the assembling tool comprising: illuminating source spacing is inserted by the fixing flat structure of assembling tool, flexible encapsulation strap in the illuminating source spacing is pressed to prevent the flexible encapsulation strap from warping. The illuminating source components and assembling tools are mounted in open of mounting frame, then the assembling tool is shifted out from the mounting frame. Thereby, the problems such as the flexible encapsulation strap warping and illuminating source welding spot falling-off on illuminating source component of LCD device are solved and assembling becomes more accurate and more labor-saving.