The invention relates to the field of electric appliances, and provides a control method and device of a double-
pipe air conditioner and the air conditioner. The method comprises the steps that after the double-
pipe air conditioner operates in a heating mode for preset time, the indoor temperature, the target temperature and the indoor
relative humidity are obtained; according to the indoor temperature and the target temperature, the type of a dehumidification mode allowed to enter is determined; determining a target dehumidification mode according to the indoor
relative humidity and the type of the dehumidification mode allowed to enter; based on the target dehumidification mode, working parameters of the double-
pipe air conditioner are controlled and adjusted; the working parameters at least comprise the conduction states of the three-way valve, the four-way valve and the
electromagnetic valve. According to the
control logic with the temperature and
humidity double-parameter criterion as the basis and the multi-valve cooperation as the means, on the premise that the
operation mode of the whole
machine is not changed, dynamic decoupling and precise cooperation of the heating function and the dehumidification function are achieved, and the constant-temperature dehumidification performance and the user experience under the high-
humidity and cold working condition are remarkably improved.