The invention discloses a use method of a welding machine for building construction. According to the method, the welding machine is connected with a power source, a water inlet switch of a cold source box is switched on, and after a cold source passes through a water flow communicator, and a controller is powered on to let equipment enter a working state; when the clod source switch is switched off, no cooling water passes through the water flow communicator, the controller cuts off the power source to make the electrode holder power-off and unavailable for normal working; when the water source of the cold source box is suddenly cut off during working, the water flow communicator can immediately transmit signals to the controller and give a note of caution to inform working staff, and meanwhile, the controller automatically cuts off the power source until the cooling water returns to normal and the whole system returns to normal, and then the welding machine returns to the working state again.