This paper presents the mathematical model of membrane current of neuron resulting from electromagnetic radiation based on the foundation of neuronal energy theory; and the effect of electromagnetic radiation on the dynamic behaviors of single neuron and the firing activities of two neurons coupled with gap connection are investigated. Results show that the neuronal firing rate is lowered as the radiation intensity increases, and finally reaches a stable value. As the radiation intensity increases, the periodical spiking of neuron is transformed into bursting firing, which is well explained based on the dynamic bifurcation theory. It turns out that the bursting firing induced by the electromagnetic radiation could spread out in neuronal network through an electrical gap junction.