The invention provides a wall-mounted air conditioner indoor unit. The wall-mounted air conditioner indoor unit comprises a shell, an air supply device, a heat exchange device, an air injection part and a fresh air device; a first air inlet is formed in the top of a case of the shell; a first air supply outlet is formed in the lower portion of a front panel; the air supply device promotes air to be sent out from the first air inlet through the first air supply outlet; the heat exchange device is arranged between the first air inlet and the air supply device so as to perform heat exchange withthe air entering the shell from the first air inlet; the air injection part is arranged below the first air supply outlet; an air injection port is formed in the edge, connected to an annular inner wall, of an annular outer wall; the fresh air device is arranged on one side of the shell and is provided with a fresh air pipe and a fresh air fan, wherein the fresh air pipe communicates with a freshair source environment; the fresh air fan enables fresh air flow to be sprayed out forwards from the air injection port so as to drive ambient air to mix with the air which is sent out by the first air supply port and is subjected to heat exchange in front of the shell. According to the scheme of the wall-mounted air conditioner indoor unit, the air supply distance can be increased, the user experience can be improved, and the air quality can be improved.