Networked predictive control (NPC) is an effective technique to compensate for transmission delays and packet dropout in networked control systems (NCS). By introducing an auxiliary error variable, in this brief, the NCS with NPC is transformed to a coupled switched system. Then, based on the switched system theory and the small gain theorem, a new stability criterion is developed under the restrictions of unstable sampling point rate. As a special case that all switched systems are Schur stable, the proposed criterion is equivalent to existing ones. The proposed stability criterion is much less conservative than existing ones, as shown from both theory and numerical simulations.