This work presents an evaluation of the Ultimate Tensile Strength (UTS) of One-sided butt-welding joints in the marine field, using the technique of the rootArc® program. The study was conducted, using a semi-automatic welding machine model; EWM-Taurus 505 Basic S. In this study, due to the developments of welding technology and the improvements in welding machines, the one-sided welding technique was adopted to weld two (S235JRG2) steel plates of 8 mm, by means of Gas Metal Arc Welding (GMAW) process. Through the experiments, six samples were evaluated. All welding passes of welded joints were welded using a welding machine (EWM) with the same program rootArc®, using 100% commercial Carbon Dioxide (Co2) as shielding gas. In addition to implementing a range of current intensity from 90 to 180 Amp and voltages from 15 to 25 Volt were used. Two different types of welding consumables electrodes were used in this work, first flux-cored wire, AWS A5.20/ASME SFA5.20 E71T-1C, and second solid wire, AWS/ASME A-5.18 ER70S-6. The experimental results were verified by Destructive Tests (DT) in the International Pipe Industry Company (IPIC) laboratory as well as Non-destructive tests (NDT), magnetic particles, Ultrasonic and X-ray, done in Port-Said Shipyard. The results have shown that the accepted joint with selected parameters was able to predict the ultimate tensile strength. Moreover, the specimen shows that the rapture due to the transverse tensile test occurs in the base metal, not in the welding seam.