This paper studies the mechanisms of ionic channels in neurons of lamprey central pattern generator (CPG), such as the N-methyl-D-aspartate (NMDA) receptor channel and the calcium-dependent potassium channel etc. The CPG properties on oscillation attributed to the ionic mechanisms are exploited. The conditions for oscillation, divergence, convergence and the guidelines on selection of the parameters are established. The effects of key parameters on CPG frequency and duty cycle are investigated. Mathematical analysis and simulation study is performed to verify these results. This study will potentially enhance the effective application of biological CPG model into engineering practice such as robotics.