The invention discloses a horizontally placed multilayer fin type heat exchanger, which comprises a heat exchanger, a combustion chamber, fins and heat exchange tubes, wherein the heat exchanger is designed as being circular, U-shaped or rectangular; multilayer fins are stacked, thereby forming the heat exchanger; the combustion chamber is arranged at the center of the fins; the fins encircling the periphery of the combustion chamber pass through the heat exchange tubes; the heat exchange tubes are serially connected from end to end, thereby forming a simple and compact heat exchange channel; and the fins of the heat exchanger are made of copper, aluminum alloy or stainless steel. The use ratio of the material is increased; the manufacturing cost is reduced; and the heat exchange area is increased.