The invention discloses a control method for a submerged-
arc welding platform for an intersection-line seam of a thick-wall large-size cylindrical weld element. The control method includes that confirming the weld element size and 
welding speed, and confirming a proper discrete step length; discretizing the intersection line to obtain coordinate values of a discrete 
welding spot; gathering an actual 
pitch angle and an actual rotating angle of the weld element through a sensor and using as two feedback quantity, comparing with 
pitch angle and rotating angle control reference values to obtain errors, using as the input of 
pitch and rotating position PID controllers, and using the output of the two position PID controllers as the speed control reference values of a roller 
drive motor and a 
hydraulic pump drive motor; comparing the three degree of freedom 
position control reference value of the 
welding gun with an actual welding gun position value detected by the sensor to obtain an error, and using the output of position PID controllers in three directions of the welding gun as speed control reference values of 
servo drive motors corresponding to three directions of a mechanical arm of the welding gun to realize 
closed loop control. The control method for the submerged-
arc welding platform for the intersection-line seam of the thick-wall large-size cylindrical weld element is capable of effectively and stably controlling the submerged-
arc welding platform for the intersection-line seam of the thick-wall large-size cylindrical weld element and enables the high-quality weld joint welding to be guaranteed.