A negative pressure wound therapy system with an alarm function for the flow rate of exudate comprises a liquid collecting bottle (5) for collecting wound exudate, a negative pressure wound therapy device (8) consisting of a negative pressure source (6) and a controller (7), and a wound kit for filling and enclosing the wound, which communicates with the liquid collecting bottle (5) via a connecting tube (4). The system further comprises a flow rate alarm processing module and an alarm warning device. If the flow rate of exudate is greater than a predefined value, the flow rate alarm processing module issues an alarm instruction. The alarm warning device sends a warning message according to the alarm instruction. If the flow rate of exudate is greater than the predefined value, the system issues an alarm instruction to the alarm warning device, by which a warning message is sent to remind medical staffs of timely inspection, thereby avoiding occurrences of serious accidents, such as the blood in human body being sucked out, and so on.