Abstarct: In this thesis the robotic gas mextal arc welding system is considered. The control of arc welding process (welding machine) and the position of welding torch are performed separately in this class of control. After introducing the gas mextal arc welding process, the kinematic and dynamic modeling and nonlinear control of SCARA robot for welding task in the work space. In addition, the requirements of robotic welding control system, especially topics of sensors and seam tracking systems are introduced. Singular states in path tracking and robot control are investigated and appropriate trajectories are designed. Various types of robot control methods in Cartesian space are presented and compared together. Nonlinear control of robot manipulator baxsed on feedback linearization for the objective of precise position and speed tracking of welding torch in order to achieve desired weld quality is presented. The effects of uncertainties in applying feedback linearization are considered and the methods to suppress these disturbances are described. The novel aspect of this thesis is the design of welding robot control system in task space in presence of uncertainties that is performed independently from arc welding process control. Total structured and unstructured uncertainties and external disturbances has been noticed and nonlinear control methods such as feedback linearization, sliding mode and fuzzy control in both joint and task space are applied in order to control the end effector of welding robot, which carries the welding torch, and these methods are compared together baxsed on tracking error in task space. In the end, performance of control system is confirmed by simulation of presented control methods on one SCARA robot.