Multi A/C is consisted of one outdoor unit and several indoor units. When the Multi Air conditioner is installed, we have to be cautious of the length of pipe arrangements. When the pipe arrangement is installed with unbalance or too long, there can be cooling capacity losses and low EER. An experimental study was carried out about the operation characteristic of Multi Air conditioner varying the length of pipe arrangements. If the pipe arrangement of the system is 15m, the cooling capacity and EER were decreased 0.8% and 1.3% respectively compared to the case when pipe arrangement is 5m. In case of 25m, the cooling capacity and EER were decreased 10.7% and 12.2% respectively compared to the case of 5m. When the length of pipe is not same each other, it is profitable to make the pipe length of highest capacity indoor unit shortest.