A full-heat fresh air blower with a double-layer air duct, the full-heat fresh air blower comprising: a fresh air duct, which communicates an outdoor air inlet with an indoor air outlet and which comprises a first downstream section; a return air duct, which communicates an indoor air inlet with an outdoor air outlet and which comprises a first upstream section; and a full heat exchange core, which comprises a fresh air passage and a return air passage that can perform heat exchange, wherein the fresh air passage is arranged in the fresh air duct, and the return air passage is arranged in the return air duct, so as to realize full heat exchange between fresh air and return air; wherein the first upstream section is located upstream of the return air passage, the first downstream section is located downstream of the fresh air passage, and part of the first downstream section and part of the first upstream section are arranged in upper and lower layers in a vertical plane to form the double-layer air duct; wherein the full-heat fresh air blower further comprises a bypass air duct which communicates with the indoor air inlet and the outdoor air outlet, wherein the bypass air duct is provided therein with a second damper configured to turn on or turn off the bypass air duct, and the bypass air duct is arranged at a periphery of the full heat exchange core, wherein a third damper is provided in the first upstream section of the return air duct; wherein when the third damper is opened, the third damper enables the first upstream section to be communicated with the first downstream section; and wherein when the third damper is closed, the communication between the first upstream section and the first downstream section can be cut off, wherein the bypass air duct is surroundingly arranged at the periphery of the full heat exchange core in a L shape, and the second damper is arranged at a corner of the L shape. a fresh air duct, which communicates an outdoor air inlet with an indoor air outlet and which comprises a first downstream section; a return air duct, which communicates an indoor air inlet with an outdoor air outlet and which comprises a first upstream section; and a full heat exchange core, which comprises a fresh air passage and a return air passage that can perform heat exchange, wherein the fresh air passage is arranged in the fresh air duct, and the return air passage is arranged in the return air duct, so as to realize full heat exchange between fresh air and return air; wherein the first upstream section is located upstream of the return air passage, the first downstream section is located downstream of the fresh air passage, and part of the first downstream section and part of the first upstream section are arranged in upper and lower layers in a vertical plane to form the double-layer air duct; wherein the full-heat fresh air blower further comprises a bypass air duct which communicates with the indoor air inlet and the outdoor air outlet, wherein the bypass air duct is provided therein with a second damper configured to turn on or turn off the bypass air duct, and the bypass air duct is arranged at a periphery of the full heat exchange core, wherein a third damper is provided in the first upstream section of the return air duct; wherein when the third damper is opened, the third damper enables the first upstream section to be communicated with the first downstream section; and wherein when the third damper is closed, the communication between the first upstream section and the first downstream section can be cut off, wherein the bypass air duct is surroundingly arranged at the periphery of the full heat exchange core in a L shape, and the second damper is arranged at a corner of the L shape.