Numerous long-span bridges have been built throughout the world in recent years. These bridges are progressively damaged by continuous usage throughout their long service life. The failure of local structural components is detrimental to the performance of the entire bridge, furthermore, detecting the local abnormality at an early stage is difficult. This paper explores a novel damage detection method for long-span bridges by incorporating stress influence lines (SILs) in control charts, and validates the efficacy of the method through a case study of the Tsing Ma Suspension Bridge. Damage indices based on SILs are subsequently proposed and applied to hypothetical damage scenarios in which one or two critical bridge components are subjected to severe damage. The comparison study suggests that the first-order difference of SIL change is an accurate indicator for location of the damage. To some extent, different levels of damage can be quantified by using SILs incorporating with X-bar control chart. Results of this study indicate that the proposed SIL-based method offers a promising technique for damage detection in long-span bridges.