An air condenser for a clothes dryer, the clothes dryer comprising a drum and a heater, the air condenser comprising condensing air ducts (j) and a cooling pipeline (i) arranged crosswise, wherein the condensing air ducts (j) comprise a first group of condensing air ducts (j) and a second group of condensing air ducts (j); air inlet ducts of the first group of condensing air ducts (j) and air outlet ducts of the second group of condensing air ducts (j) are at least partially arranged in a heat exchangeable manner; and air outlet ducts of the first group of condensing air ducts (j) and air inlet ducts of the second group of condensing air ducts (j) are at least partially arranged in a heat exchangeable manner; characterized in that: the condensing air ducts (j) comprise intermediate air ducts; at least one part of the intermediate air ducts is connected between the air inlet ducts and the air outlet ducts of the first group of condensing air ducts (j); at least another part of the intermediate air ducts is connected between the air inlet ducts and the air outlet ducts of the second group of condensing air ducts (j); and the intermediate air ducts and the cooling pipeline (i) are arranged crosswise to perform heat exchange; wherein a low-temperate dry air or liquid before passing the air condenser enters the air condenser from an inlet of the cooling pipeline (i) and performs heat exchange with saturated hot air coming from inside the drum and entering the condensing air ducts (j) before passing through the air condenser, wherein the saturated hot air comes from the drum and enters the air condenser from first air inlets of the first group of condensing air ducts (j) and second air inlets of the second group of condensing air ducts (j) to perform heat exchange to become unsaturated hot air, and the unsaturated hot air is discharged from the air condenser from first air outlets of the first group of condensing air ducts (j) and second air outlets of the second group of condensing air ducts (j) to be collected together to enter the heater to be heated; wherein the air condenser comprises two types of heat exchange, one of which is performed between air in the first and second groups of condensing air ducts (j) and dry air or liquid in the cooling pipeline (i), the other of which is performed between air in the first group of condensing air ducts (j) and air in the second group of condensing air ducts (j). the condensing air ducts (j) comprise intermediate air ducts; at least one part of the intermediate air ducts is connected between the air inlet ducts and the air outlet ducts of the first group of condensing air ducts (j); at least another part of the intermediate air ducts is connected between the air inlet ducts and the air outlet ducts of the second group of condensing air ducts (j); and the intermediate air ducts and the cooling pipeline (i) are arranged crosswise to perform heat exchange; wherein a low-temperate dry air or liquid before passing the air condenser enters the air condenser from an inlet of the cooling pipeline (i) and performs heat exchange with saturated hot air coming from inside the drum and entering the condensing air ducts (j) before passing through the air condenser, wherein the saturated hot air comes from the drum and enters the air condenser from first air inlets of the first group of condensing air ducts (j) and second air inlets of the second group of condensing air ducts (j) to perform heat exchange to become unsaturated hot air, and the unsaturated hot air is discharged from the air condenser from first air outlets of the first group of condensing air ducts (j) and second air outlets of the second group of condensing air ducts (j) to be collected together to enter the heater to be heated; wherein the air condenser comprises two types of heat exchange, one of which is performed between air in the first and second groups of condensing air ducts (j) and dry air or liquid in the cooling pipeline (i), the other of which is performed between air in the first group of condensing air ducts (j) and air in the second group of condensing air ducts (j).