Based on the engineering background of a long-span suspension bridge with a main span of 500 m, the buffeting response of a long-span flexible suspension bridge under fluctuating wind loads is analyzed and calculated, and some useful conclusions are obtained. Modal analysis shows that the natural vibration frequency of long-span suspension bridge is low, which is a typical wind-sensitive flexible structure. When the buffeting force and self-excited force are considered at the same time, the maximum buffeting displacement response of the main beam of the suspension bridge can be obtained according to the extreme value theory. The results show that the maximum buffeting displacement response in the vertical, horizontal and torsional directions all occur in the middle of the main span, and the value is large, which cannot be ignored in the structural design.