The rate of injecting packets into the network should be regulated carefully because the packet latency could increase rapidly if the network saturated. In order to solute this problem, we present a new flow control strategy which can be coupled with any routing algorithm. In particular, we introduce the notion of Injection Level, a set of values of injection rate. We expect to simplify the process of flow control by applying a group of predefined injection rates according to the status of the network. The performance of the strategy is evaluated by a flit-accurate and open source simulator. Results show that the NoC could avoid the saturation problem successfully.