Abstract: The distribution of as-welded residual stresses in titanium-bearing low-carbon high-strength steel exhibiting two controlled initial plate temperatures (7 and 25 °C) was measured and calculated under the same heat input. The as-welded plate containing the cooling system at 7 °C exhibited a higher residual tensile stress than the as-welded plate did at room temperature (25 °C) because of the greater temperature gradient in the 7 °C system. The diamond-like carbon (DLC) thin-film coating was examined after welding and confirmed using the Raman spectrum. The successful DLC thin-film deposited on the as-welded plates further reduced and relaxed the magnitude of the surface residual stress of weld caused by the cathodic arc physical vapor deposition process. The distributions of the measured surface residual stresses on weld correspond with the finite element method simulated results.