An inflatable decorative system, comprising: an inflatable hollow bag body (10, 210) defining a line hole and comprising an inflation port; a plurality of first fixing portions (13, 213, 13') arranged on an inner surface of the bag body (10, 210), each first fixing portion (13, 213, 13') having a perforation or a hook portion; and a light string system; wherein at least an end portion of the light string system extends out of the bag body (10, 210) through the line hole, and the remaining portions of the light string system are arranged inside the bag body (10,210) and fixed among the plurality of first fixing portions (13, 213, 13') so that the light string system is unfolded into a preset shape in the bag body (10, 210) after the bag body (10, 210) is inflated, characterized in that the inflatable decorative system further comprises: at least one intermediate fixing portion (20, 20', 20", 20'''); and a plurality of strips or lines (30, 230); wherein the plurality of strips or lines (30, 230) are connected between the at least one intermediate fixing portion (20, 20', 20", 20'") and the plurality of first fixing portions (13, 213, 13'), or are simultaneously connected among the plurality of first fixing portions (13, 213, 13'), and the plurality of intermediate fixing portions (20, 20', 20", 20'") when the inflatable decorative system is provided with the plurality of intermediate fixing portions (20, 20', 20", 20"'); and the plurality of strips or lines (10, 210) are unfolded into a second preset shape after the bag body (10, 210) is inflated and can limit a maximum size of the bag body (10, 210); wherein said at least one intermediate fixing portion (20, 20', 20", 20"') is suspended inside the hollow bag body (10, 210), when the bag body (10, 210) is inflated. an inflatable hollow bag body (10, 210) defining a line hole and comprising an inflation port; a plurality of first fixing portions (13, 213, 13') arranged on an inner surface of the bag body (10, 210), each first fixing portion (13, 213, 13') having a perforation or a hook portion; and a light string system; wherein at least an end portion of the light string system extends out of the bag body (10, 210) through the line hole, and the remaining portions of the light string system are arranged inside the bag body (10,210) and fixed among the plurality of first fixing portions (13, 213, 13') so that the light string system is unfolded into a preset shape in the bag body (10, 210) after the bag body (10, 210) is inflated, characterized in that the inflatable decorative system further comprises: at least one intermediate fixing portion (20, 20', 20", 20'''); and a plurality of strips or lines (30, 230); at least one intermediate fixing portion (20, 20', 20", 20'''); and a plurality of strips or lines (30, 230); wherein the plurality of strips or lines (30, 230) are connected between the at least one intermediate fixing portion (20, 20', 20", 20'") and the plurality of first fixing portions (13, 213, 13'), or are simultaneously connected among the plurality of first fixing portions (13, 213, 13'), and the plurality of intermediate fixing portions (20, 20', 20", 20'") when the inflatable decorative system is provided with the plurality of intermediate fixing portions (20, 20', 20", 20"'); and the plurality of strips or lines (10, 210) are unfolded into a second preset shape after the bag body (10, 210) is inflated and can limit a maximum size of the bag body (10, 210); wherein said at least one intermediate fixing portion (20, 20', 20", 20"') is suspended inside the hollow bag body (10, 210), when the bag body (10, 210) is inflated.