Aiming at the vibration problems of air-condition pipes, the finite element calculation model of air-condition pipes is established. On the basis of modality analytical theory of vibration structure, the modality characteristics of the air-condition pipes is analyzed. Taking the result of modality analysis as a basis, the influences of the pipes chickness and counterweight on the air-condition pipes modality are analyzed respectively, and suggestions on the air-cond ition pipes structural design are put forward, thus it is possible to avoid the pipes cracking caused by vibration, which may result in the leaking of coolant. The suggestions can provide references to this kind of analysis.