The invention provides a congestion judgment method in a loss-free network. The method comprises the following steps of pausing sending of a data packet when a PAUSE frame of a next-hop device arrives; when a RESUME frame of the next-hop device arrives, recording the number of the data packets in a current sending queue as the reference number, and recovering the sending of the data packet; and after the number of the sent data packets exceeds the reference number, acquiring a first congestion detection index when each data packet is sent continuously, and if the first congestion detection index exceeds a first preset threshold, carrying out congestion marking on the sent data packet. According to the embodiments of the invention, the defects that the accuracy is low and the flow independent of the congestion is easily influenced due to the fact that whether a congestion mark is added to the data packet is judged only according to the length of the queue are overcome, the defects thatPFC is easy to generate a congestion tree and is rapidly expanded are overcome, the method has an advantage of being more accurate in adding the congestion mark, and a foundation is provided for further judgment and congestion processing of the congestion flow.