We propose a model to discribe the effect of divalent cations on the activation processof Na─channels.The following are the results obtained from the model: For the activation pro-coss of Na─channels there exists a threshold of depolarization voltage;The increass of concen-tration of divalent cations results in increase of the threshold; The relaxation time of activationprocess and the maximum degres of activatcatcation are significantly related with the concentra-tion of divalent ions and with the depolarization voltage

The results mentioned above agree wellwith those obtained through experiments qualitatively and semi─quantitatively.