In order to investigate the influence of a mid-tower on the buffeting performance of a long-span triple-tower suspension bridge with continuous span, the first triple-tower suspension bridge in the world, the Taizhou Bridge, is taken as the research object. The influences of the type and longitudinal stiffness of a mid-tower on wind-induced buffeting responses of the long-span triple-tower suspension bridge with continuous span are studied using structural nonlinear time-domain analysis accompanied by a finite element model. The comparison between calculated and measured modal parameters of the Taizhou Bridge validates the accuracy of the established finite element model. The results show that an A-type mid-tower can significantly decrease the torsional buffeting displacements of the main girder with slightly suppressed vertical and lateral displacements when compared to a herringbone type mid-tower. Increasing the longitudinal stiffness of the mid-tower can decrease the vertical and torsional buffeting displacements of the main girder to some extent, while hardly affecting the lateral displacements. Variation in the longitudinal stiffness of the mid-tower has feeble influence on the translational buffeting displacements of the side tower. The torsional displacement and displacement along the bridge deck are prominently decreased with the increment of longitudinal stiffness of the mid-tower with limits. Meanwhile, increased longitudinal stiffness of the mid-tower will slightly augment the torsional buffeting displacement of the side tower, and can positively suppress lateral buffeting displacement of the mid-tower to some extent.