Abstract: The arc pressure during horizontal variable polarity gas tungsten arc welding(VPTIG) was measured by pressure transducer under different welding conditions. The radial distribution of arc pressure was investigated, and the central arc pressures for DC TIG welding and VPTIG welding with a period of 5% and 15% for direct current electrode positive(DCEP) were compared. The experimental results showed that the radialdistribution of VPTIG pressure was hyperbolic. When the welding current was in the range of 100 A to 140 A and with the same root mean square value, the arc pressure decreased gradually with the increase of time ratio of DCEP at one cycle during DC TIG welding and VPTIG welding with a period of 5% and of 15% for DCEP, due to the difficulties of electron emission and arc divergence in the period of DCEP. And the integrated arc force was directly proportional to the square of welding current.