To study the random seismic response of long-span cable-stayed bridges at different sites，the site transfer function was used to evaluate the influence of different site conditions on ground motion propagation.By considering the traveling wave effect and the coherence effect，the multi-point power spectrum under different site conditions was generated.By using the pseudo excitation method for solving the absolute displacement，the seismic responses of cable-stayed bridges under uniform excitation and multi-dimensional and multi-point excitation at different sites were compared.A long-span cable-stayed bridge was selected as an example，and Ansys finite element software was used to analyze the random seismic response of the bridge.By considering the influence of site conditions on the seismic power spectrum，the random responses of the bridge under different excitation modes were calculated，and the power spectrum of each element of the bridge was extracted.The extreme root mean square of the power spectrum response was calculated.The results show that the amplification effect of soft soil on the random response of the bridge is about three times that of hard soil，and the amplification effect of multi-point excitation on the random response of the bridge is about 1.5 times that of uniform excitation.Therefore，the site effect has a great influence on the random seismic response of long-span cable-stayed bridges，and its influence cannot be ignored in bridge design.