Nonlinearly evolutionary process of damage due to material degradation is not considered in the seismic performance design of complex high-rise structure.Aiming at complex high-rise steel-concrete composite structure,the time-dependent characteristic of local component and whole structure induced by key parameters of concrete material was considered in this paper.Combining the time-dependent model of seismic damage with dynamic elastic-plastic time history analysis method,damage time-dependent characteristic of high-rise steel-concrete composite structure was studied.Because key parameters such as stiffness and damping not only have the “variable” character in service periods,but also have the “constant” character under seismic loads,the method regarding the key parameters as “quasi-variables” was proposed.Dynamic elastic-plastic time history analysis was used to obtain the dynamic response of the structure.Both the integral method based on interlayer displacement and the weighted combination method based on component’ damage were used to research on the time-dependent characteristic of the composite structure.The result shows that the structure in service period has significantly time-dependent characteristic.Time-dependent damage might exceed the corresponding threshold value under frequent earthquakes.The change of stiffness may lead to the change of the lateral force and the transmission capacity of earthquake action.Compareing the time-dependent damage in service period with design value without counting the time-dependent characteristics,it can be found that time-dependent characteristics of material have great influence on the accuracy of the seismic design and evaluation of the structure.