The present invention discloses a congestion controlling method, which comprises the following steps: (1) a cell is input into a buffer area, to record relative parameters, and the average leakage rate f of the cell is calculated in a general way according to the parameters; (2) according to the average leakage rate f of the cell, the reasonable leakage amount of the cell at the current time is calculated, and the leakage of the cell inside the buffer area is controlled according to the calculated amount; (3) a corresponding weighted processing way is selected to process the average input rate of the cell, and then the relative parameters are reset to return to step (1). The method of the present invention reflects the long-term changing trend of the average rate of the cell input, and restraints the jitter of the rate output to the maximum limit, meanwhile weights the input rate of the resent time, to reflect the latest cell input condition and to fit the conditions of flow cut-off and fluctuate bit rate, etc. The user can choose different sizes of the leaked barrel buffer areas and the weighted parameters according to the type of the service, to meet the needs of different users.