The YangPu Bridge was the longest among the same type of suspension bridges in the world at the time of construction. In order to identify its operative performance and ensure safe operation

a lot of money and work time have been spent in the maintenance of this bridge every year. This paper focuses on how to develop a more efficient and economical procedure for bridge maintenance. The ARMA model is employed and some seismic frequencies and damping ratios are obtained from data of random vibration of the bridge. After an earthquake

a typhoon

or some long duration of operation

variations in these frequencies and damping rations are checked

on which bridge maintenance is based. It is demonstrated from the preliminary results that the proposed method is applicable for maintenance of the main towers of the bridge.