The thermal performance of a flat-strip heat pipe with inner grooves and the screen mesh cover was investigated experimentally. The heat pipes were made of 2024 aluminum alloy of which the dimensions were 30 (W) $ imes$ 4 (T) $ imes$ 150 (L) mm. The cross sectional dimensions of inner groove were 0.4$ imes$0.9 mm and the space between grooves was 0.6 mm. To enhance the capillary force, foe screen meshes were attached to cover the grooved inner surface. In the grooved heat pipes without screen mesh cover, the maximum thermal load of 180 W (12 W/$cm^2$) was achieved for operating temperature below $130^{circ}C$ at horizontal position. The heat pipes with screen mesh cover showed the thermal resistances less than one third of those without screen mesh cover, and showed less fluctuation in the thermal resistance values. Furthermore, the thermal performance of the former exhibited less dependence on the tilt angle and the fill charge ratio.