Abstract: In this paper,the method and apparatus used to measure the arc force produced during welding with covered electrodes were studied and developed.The factor which caused the main error of measurement was revealed,and the results of measuring were corrected.The arc force of typical electrodes under different welding conditions were measured and the factors affecting the forces were also investigated.Furthermore, the effect of each single component of the electrode covering,such as marble, feldspar,and fluorspar,on the arc force was studied;and the origin of arc force in MMA welding with covered electrodes was preliminarily analyzed.