The invention belongs to the field of printing equipment, and particularly relates to an automatic detection type ink supply system for a printer. The automatic detection type ink supply system for the printer comprises a printing roller set, an ink box and an ink supply pump. An ink inlet pipe and an ink outlet pipe are connected to the ink supply pump. A controller and a flow sensor are mounted in the ink box. The controller is connected with the flow sensor and the ink supply pump. A gun nozzle is arranged at the ink outlet end of the ink box. The gun nozzle is of a rectangular structure and corresponds to the printing roller set. The controller is used for controlling the flow sensor, when the ink flow exceeds a set flow value, the controller controls the ink supply pump to stop supplying ink, and thus ink in the ink box is prevented from exceeding a certain liquid level; and under the influence of the acting force generated when the printing roller set rotates, the ink in the ink box can fluctuate and thus is prevented from overflowing out of the ink box.