A roll-up cover assembly includes a cover assembly comprising first and second side rails and front and rear bumpers, as well as a cover, wherein a lower portion of an inner side of the first side rail is provided with a slideway, an adjustment base, an adjustment screw, an adjustment knob, a receiver; the adjustment base is fixed inside the first side rail and can not be moved; the adjustment base is provided with the adjustment knob thereon, the adjustment screw passes through the adjustment base and the adjustment knob, and an end part of the adjustment screw is snap-fixed into a groove on the receiver; the receiver is a separated-type structure, wherein both of the upper and lower portions are fixed onto the slideway, and when the adjustment knob is turned, the adjustment screw produces a displacement and drives the receiver to slide within the slideway.