Time-sensitive networking (TSN) standards can provide high bandwidth and low latency for communication. Schedulability analysis under mechanism combinations needs to be studied. Under cyclic queuing and forwarding (CQF) with preemption, this letter analyzes the traffic transmission process and defines the traffic classes. Then, this letter provides a schedulability analysis on streams of all traffic classes. The results can provide the network designers with guidelines in the configuration under CQF with preemption and accelerate the usage of TSN for safety-critical communication scenarios.