The invention discloses a large forged piece compressed electric arc and induction composite heat source repair welding device and a method thereof. The repair welding device comprises a six-axis robot, a handling frame which can move up and down and backwards and forwards, a work table and a welding gun, wherein the six-axis robot is arranged on the handling frame; an inductor and the welding gun are arranged on the robot; a temperature sensor is arranged aside the inductor; and the welding gun can generate compressed electric arcs. The repair welding method comprises the following steps: firstly, preparing a protectant for repair welding and deposited metals according to material compositions of a large forged piece; secondly, presetting a program and related parameters; thirdly, placing the protectant on a repair welding area, and performing induction heating on the repair welding area; fourthly, acquiring the temperature of the repair welding area, judging whether the preset valueis reached, and performing continuous heating if the preset value is not reached; fifthly, removing the inductor after the heating is over, and igniting the compressed electric arcs for starting welding; and sixthly, performing induction heating after the welding is over. The invention realizes preheating before repair welding, and the strength of a repair welding joint is more than that of the deposited metals.