The invention provides a judgment method of a connecting relation between 
signal control lines of indoor and outdoor units and connecting pipes, a judgment device of the connecting relation between the 
signal control lines of the indoor and outdoor units and the connecting pipes and a multi-split air conditioner. The method comprises the steps: detecting the real-time temperature of an 
evaporator of any indoor unit after a 
refrigeration signal is sent to any indoor unit of a plurality of indoor units of the multi-split air conditioner; judging whether the real-time temperature of the 
evaporator of any indoor unit changes, when the real-time temperature of the 
evaporator of any indoor unit changes, the connecting relation between the signal 
control line between an outdoor unit and any indoor unit of the multi-split air conditioner and one connecting 
pipe is matched, and if the real-time temperature of the evaporator of any indoor unit does not change, the connecting relation between the signal 
control line between the outdoor unit and any indoor unit and the connecting 
pipe is not matched. Through the judgment method, the judgment device and the multi-split air conditioner of the technical scheme of the invention, in the condition that the outdoor unit and the indoor units are not removed, the 
control logic of output signals of the signal control lines is directly changed, so that the signal control lines and the connecting pipes are matched, so as to correctly control the indoor units.