The invention provides a wall-mounted air conditioner indoor unit, an air conditioner and a control method. The indoor unit comprises a machine shell, a draught fan, an evaporator and a purification module. An air flue is defined in the machine shell. The machine shell is provided with an air inlet, a purification air inlet and a temperature adjusting air inlet which are communicated with the air flue. The machine shell is further provided with an air inlet pipe opening and closing the temperature adjusting air inlet. The draught fan is arranged in the air flue. The evaporator is arranged in the air flue. The purification module is arranged in the air flue and used for purifying air entering the air flue through the purification air inlet. By means of the purification air inlet and the temperature adjusting air inlet, different air inlets can be utilized when the air conditioner carriers out purification and temperature adjustment, the purification module is arranged in the air flue at the purification air inlet, it is guaranteed that the air conditioner is not subjected to the air resistance caused by the purification module during temperature adjustment, and it can be avoided that the size of the indoor unit is increased due to the action of the purification module.