This paper performs results of study on effects between the breadth of butted plate and an angular distortion while welding of ship hull, all experiments are conducted on the R-31/PA welding procedure with different breadths of butted plate. The result shows that: the angular distortion along cross section of butted plate are different, if the breadth of butted plate is increased, the angular distortion will be reduced and contrary. In case the breath of butted plate exceeds 500 mm, the cross section of butted plate has parabol profile on the range from the center to 40 mm of plate-breadth, from 40 mm to 60 mm of plate-breadth the profile is opposite bending, remaining of butted plate is similar of angular distortion. Simultaneous, the experimental results are not satisfy with the Okerblom's formula.