Abstract: Based on summarizing theoretical and experimental research results,the practical method is presented for seismic analysis of reinforced concrete frames considering interaction between primary and secondary structures,with the emphases on how to consider interaction between cast-in-situ beam-slab system as well as infilled walls and main frames.And then,taking a modern building with cast-in-situ reinforced concrete structure for example,the effects of interaction between primary and secondary structures on seismic appraisal of existing buildings are analyzed.The example analysis shows that after considering the interaction between cast-in-situ beam-slab system as well as infilled walls and main frames,the stiffness and strength potential of existing structures are fully utilized,the computing structural stiffness is increased distinctly,the computing displacement response is declined rapidly,the seismic bearing capacity is improved evidently,and the evaluating conclusions of safety and seismic behavior are more reasonable and accord with the practical effects.