respectively and the object is fixed in the fixed holes 32 of the slide base 30 and permitted to move along the u shaped guide track 20 referring to fig2 3 fig2 is a perspective view of the length expandable linear guideway in accordance with the first embodiment of the present invention showing an expanded status fig3 is a perspective view corresponding to fig2 of showing a contracted status of the length expandable linear guideway of the present invention the u shaped guide track 20 is movable within the base guide track 10 and the slide base 30 is also movable within the u shaped guide track 20 thereby the guiding travel of the length expandable linear guideway in accordance with the present invention equals the moving travel of the u shaped guide track 20 within the base guide track 10 plus that of the slide base 30 within the u shaped guide track 20 viz the moving travel of the expandable linear guideway of the present invention is two times longer comparing with the original one when the u shaped guide track 20 moves back into the base guide track 10 and so does the slide base 30 move back into the u shaped guide track 20 simultaneously so that the base guide track 10 u shaped guide track 20 and slide base 30 may be superposed one another thereby the length of the length expandable linear guideway in accordance with the present invention is shortened that is to say the install space is saved on the other hand in order to allow the slide base 30 and the u shaped guide track 20 to expand from the u shaped guide.