The effect of TIG (tungsten inert-gas arc) dressing on fatigue strengths and low temperature properties of welded joints in support of the fillet weld of offshore platform was studied experimentally. The fatigue strengths and the lower temperature properties are found being improved greatly by using TIG dressing. However, the effect depends on TIG dressing technique and specification. In order that test results will be comparable, five sets specimens used by TIG dressing and one set specimens without dressing have been investigated on the fatigue test and drop hammer test. The estimating formula of fatigue life is derived and the S—N curves are obtained. Therefore the optimum parameters of the specification and the technology are determined. The fatigue strengths used by TIG dressing have increased by 189%. The mechanical properties in low-temperature have been improved greatly by TIG dressing also. The brittle transition temperature of specimen used by TIG dressing has been lowered 70℃. The TIG-dressing technique has been tested in offshore drilling platform and the fatigue life by TIG dressing has been greatly improved. So the above technology is quite effective.