Coherence resonance in the Chay neuron model with noise in the slow dynamics is studied. Noise that is added to the slow dynamics amounts to calcium ionic fluctuation. So it is more biologically feasible. We find that the output signal-to-noise(SNR) of the Chay neuron system goes through a local maximum with increasing noise intensity at optimal noise level, which shows the occurrence of coherence resonance. Consequently the noise in the slow dynamics , namely, calcium ionic random fluctuation may enhance signal detection and transduction.