The invention discloses a flat slide-up sectional bar of a thermal-insulation sliding window and relates to the field of building materials. The flat slide-up sectional bar comprises an inner parted body and an outer parted body which are connected together through two clamping parts, the inner parted body comprises a center cavity with the four faces closed, the outer wall of the upper end face of the center cavity is provided with a right-angle clamping side, the outer wall of the lower end face of the center cavity is provided with a sliding rail sealing baffle stretching downwards and a center sliding rail, and the outer wall of the right side face of the center cavity is provided with two clamping part grooves; the external structure of the outer parted body is the same as that of the inner parted body, and the outer parted body and the inner parted body are oppositely arranged. The flat slide-up sectional bar is simple in structure, reasonable in design, convenient to construct and install, safe and environmentally friendly in use, high in production efficiency, low in cost, good in sealing performance, low in noise and capable of being widely applied to alloy sliding sashes, and components can not deform easily.