Abstract: To examine the damping ratio and its influence on seismic response of the maintenance hangar, firstly,the equivalent structures concept,which is through potential energy and damping ratio shared by structural members with different materials,was used to obtain the damping ratio.Additionally,the related program was developed.According to the program,the damping ratio for the interest structures with three kinds of span is determined.Meanwhile,the value of damping ratio which varied with the stiffness change by the RC columns was discussed.Finally,based on two kind of damping ratio,such as value calculated from method mentioned in the paper and value selected in practical design,the difference of the seismic response from two types damping ratio are compared.It is shown that the damping ratio of double-layer diagonal on diagonal space frame supported by the RC columns is below 0.023 5,which is smaller than the 0.03 damping ratio for the current practical design.Therefore,the damping ratio should be analyzed specifically for evalu- ating the dynamic behavior of hangars.The stiffness of the RC columns has minor impacting on the damping ratio.For practical design,if the span of hangar is larger than 100 m,0.023 would be reasonable damping ratio.The seismic responses calculated with calculating damping ratio are 10%~20% larger than the result from damping ratio for practical design.