This paper studies the seismic performance evaluation method of existing structures.Firstly

mechanical model of the structure in service is given based on previous studies.Secondly

the most disadvantageous direction of structure is obtained through two small earthquake time-history analyses

and the pushover analysis is carried out in this direction using three-dimensional analysis program CANNY99.Finally

the structure performance point for seismic performance assessment is gained by superimposing the structure curves onto the actual demand spectrum of seismic wave.The procedure of the proposed method is performed through a specified example.The destruction of the beams which reach performance point is simulated by program.In this paper

the impact of service life on structure is considered based on the research of steel corrosion and concrete aging.At the same time

the pushover analysis of the structure is carried out in consideration of the most disadvantageous direction.The proposed method considers the characteristics of two-way bent of the columns and is proved to be more practicable.