Because the property of a class of W state can be used as entanglement channel for realizing perfect teleportation and dense coding with the successful probability 100%, a simple scheme is presented for generating this W-class entangled state. It relies on the superconducting quantum interference devices (SQUIDs) simultaneously interacting with single-mode cavity field under resonant circumstances. The distinct feature lies in that the whole course of preparation only needs one step. The scheme can be implemented by the present cavity QED techniques.