The application discloses a composite passive window and a mounting method thereof, which comprises a first frame, a third frame, a second spacing strip, a third spacing strip, second heat insulation filling cotton, a second frame, a fourth frame, a first spacing strip, a fourth spacing strip, first heat insulation filling cotton, a first sealing element, a second sealing element, a fifth frame, glass, an outer frame
assembly, heat insulation filling, a fixing
assembly, a limiting
assembly and a third sealing element. The composite passive window has excellent heat insulation performance, simple overall structure and is easy to assemble and use. The heat insulation filling is filled in the outer frame assembly to block the
heat transfer between the indoor and outdoor, and two heat preservation lines are formed in the cross section in a non-exposed mode through the fifth frame, so that the heat insulation performance of the aluminum
alloy window is improved without changing the width of the middle spacing strip of the broken bridge aluminum
alloy profile, and the durability and stability of the whole window under the new
structure system are ensured.