An air-sealed body with automatically opened air valves and a manufacturing method thereof uses a heat resisting material to spread between two inner films. The two inner films are stacked together between two outer films and heat sealed with the outer films to form an air passage and plural air columns therein. Air inlets and heat-sealed blocks are both formed by heat sealing, wherein each heat-sealed block is shrinking gradually from one side thereof near the first transverse heat-sealing line to another. During filing air the two outer films around the air passage are pulled apart in a longitudinal direction, and the air passage will be contracted in a transverse direction and then the two inner films are pulled apart in a longitudinal direction to open the air inlets. Thereafter, after entering the air columns, the air presses the two inner films to close the air columns.