This document describes a priority-based spectrum sensing and security system using radio cognitive networks. The proposed system aims to efficiently access spectrum sharing between primary users and secondary users. It uses cognitive radio to detect available channels and allot unused licensed primary spectrum to secondary users. The system uses a spectrum sharing algorithm to store the status of ideal primary channels in a priority queue. This allows secondary users to access ideal channels efficiently while avoiding interference with primary users. The results show that the system can perform both spectrum sensing and data transmission/receiving functions effectively with low power consumption.