The rules of seismic response of largespan columnfree metro station under uppersoft and lowerhard composite strata are studied by software ABAQUS based on Guangzhou Metro Line No. 11. Six cases are set with interface between soft and hard strata horizontally implemented in different positions of station structure. And comparisons on seismic response of structure among different cases are analyzed. The results show that: 1) As interface positioning above or below middle slab of station structure, seismic response, i.e. damage degree, maximum relative horizontal displacement, residual deformation and shaking form, are distinguished under strong seismic. 2) With increment in peak acceleration of seismic wave, variation of structure′s seismic response caused by interface′s position gains more augmentation when interface positioning above middle slab than below. 3) Amplification coefficient of acceleration between roof slab and bottom slab is closely related to size of seismic as well as thickness of soft stratum. 4) Ratio of shear modulus between different strata has an effect on seismic response of metro structure to a certain degree. When ratio is smaller than 1/40, stabilization is observed on the difference of seismic response.