Abstract: Objective In order to further improve welding efficiency and welding quality of pipeline, twin-wire single-arc gas shielded welding technology is expected to be applied in pipeline welding. Methods In the test process, control variable method was used to carry out twin-wire single-arc gas shielded welding test, and variation coefficient of welding heat input and weld formation coefficient were used as indexes to study influence of welding parameters on arc stability and weld formation of twin-wire single-arc gas shielded welding technology. Results The stable welding parameter range of twin-wire single-arc gas shielded welding was obtained through the test, and test results were as follows, wire spacing of 0 mm, wire extension of 11～19 mm, wire feeding speed of 10～14 m/min, voltage correction of −3～−1 and pulse correction of −4～0. The test results obtained the effect of different welding parameters on weld formation, and molten drop transfer form was projected transfer with a drop per pulse. Conclusion The evaluation method using variation coefficient of welding heat input as an indicator is a rational and effective method of determining welding parameters.