The invention provides a method and a system for adjusting the train braking force according to the train running speed. The method for adjusting the train braking force according to the train running speed comprises the steps of: obtaining target deceleration according to the level of braking and the acquired current train running speed; acquiring the weight of a train and obtaining target braking force according to the weight and the target deceleration; and using the target braking force to drive a braking execution mechanism to execute braking. The method and the system for adjusting the train braking force according to the train running speed provided by the invention have the advantages that since different braking forces can be output to the braking execution mechanism in real time according to the current train running speed and the weight of the train, not only can the safe braking distance be ensured, but also the damages to wheels and braking parts can be avoided, the maintenance cost of the train is reduced, the braking process is enabled to be more stable, and the safety is higher.