The pre-tightening force is the key factor to resist external load in a connection, and its magnitude directly affects the stiffness and fatigue life of the connection. The Shiyang Bridge, a long-span steel truss suspension bridge, was taken as the support project. Aiming at the problem that the traditional bolt connections were prone to loosening under load, the group riveting effect of short-tailed ring groove rivets and the preload relaxation behavior after riveting were studied. Through a full-scale model test of chord ring groove rivets, the distribution of preload, the influence of riveting sequence on preload, and the law of preload relaxation after riveting were systematically investigated. The results showed that the pre-tightening force of the ring groove rivet was normally distributed in the range of 310~350 kN, which was significantly higher than the design value of high-strength bolts of the same type, and met the specification requirements. The riveting process can cause pre-tightening force attenuation. The sequence of cross-riveting from the center of the rivet cluster to the periphery resulted in a smaller degree of pre-tightening force attenuation. The rivets in the center area of the group riveting were most affected. During the 1600 hours monitoring period, the preload attenuated by an average of 2.57%, which still met the design requirements after relaxation. The preload loss caused by the riveting process was more significant than that caused by rivet relaxation.