Combination of a Roof Top Air Conditioning Unit

A combination of a roof top air conditioning unit, the combination comprising a roof top unit, a roof, connection air ducts and an air distribution box, wherein the roof top unit is disposed on an outer wall surface of the roof, the roof top unit having a base pan provided with an air outlet; the air distribution box disposed on an inner wall surface of the roof, the air distribution box provided with an air inlet upper duct; the plurality of connection air ducts communicating the air outlet of the roof top unit with the air inlet upper duct of the air distribution box via the opening of the roof, characterized in that an adjustment portion for adjusting a roof thickness gap is provided around the air outlet of the base pan. This combination simplifies the complexity of assembly, such that the mounting process is simpler, and thus the cost is also reduced.