The utility model relates to the technical field of curtain boxes, in particular to a width-adjustable adaptive curtain box. The width-adjustable adaptive curtain box can be flexibly adjusted according to the width of a window, the installation efficiency is improved, material waste is reduced, and it is ensured that the curtain box is well matched with the window. A width-adjustable adaptive curtain box comprises a front baffle, an upper baffle, a connecting baffle, a connecting plate and the like, the upper side of the front baffle is connected with the upper baffle, the right side of the upper baffle is detachably connected with the connecting plate through a plurality of fixing bolts, and the right side of the connecting plate is detachably connected with the connecting baffle through a plurality of fixing bolts. According to the size of a window, the fixing bolt is taken down, the distance between the upper baffle and the connecting baffle is adjusted through the connecting plate so as to adapt to windows of different sizes, and the effects that flexible adjustment can be achieved according to the width of the window, installation efficiency is improved, material waste is reduced, and it is ensured that the curtain box is well matched with the window are achieved.