A method for purifying an air pollution in an indoor space to a level close to zero includes providing an indoor leaking detection for blocking an outdoor air from entering the indoor space; and providing an indoor monitoring system including plural gas detection devices (A, 3), a central controlling monitor (B) and plural air-exchanging filtration devices (C), wherein the gas detection devices (A, 3) detect the property and concentration of the air pollution and output outdoor/indoor air pollution data, the central controlling monitor (B) receives the outdoor/indoor air pollution data, performs an intelligent computation to compare thereof and determine an air pollution location, and issues a control instruction, and the air-exchanging filtration devices (C) receive the control instruction and perform an enabling and adjusting mechanism for guiding the air pollution to pass through the air-exchanging filtration devices (C) for being purified to a level of zero or close to zero, thereby cleaning the air pollution to a breathable state.