Servo gun is a new type of welding gun based on servo motor controlling of the electrode. Precision and electrode force controlling characteristic of servo gun was studied in order to make servo gun be greatly applied in autobody manufacturing. The study shows that transmission error and returning error of servo gun can meet the requirement of electrode displacement online inspecting. Electrode force controlling characteristic between servo gun and air gun was compared and analyzed. The result shows that on contrast to air gun, servo gun has even smaller impacting force on part, reaches less squeezing time at squeezing stage, and has more accurate electrode force controlling ability, less thermal undulate electrode force at welding stage, which can benefit to nugget formation and make the criterion of welding technology based on electrode force controlling be possible.