In multi-user multi-channel cognitive radio networks for the internet of things (CR-IoT), a spectrum co-sensing-allocation strategy based on edge computing is proposed. To evaluate the performance of the proposed strategy, a performance evaluation system (PES) capable of quantifying the quality of service (QoS) of cognitive users and the interference to primary users is developed. In the PES, a Markov model is established to describe the CR-IoT system state based on queuing theory. The performance metrics of heterogeneous cognitive users with configurable parameters can be analyzed independently. Thus, various spectrum sensing-allocation strategy can be evaluated using the proposed PES. Numerical results show that the proposed edge computing strategy outperforms central computing strategy in QoS of cognitive users and the quantified interference to primary user. It proves that the PES can help regulators design various spectrum sensing-allocation strategy.