Experimental　records　in　the　cerebral　cortex　indicate　that　ammonia　injection　can　lead　to　seizures.　Considering　that　astrocytes　play　a　vital　role　in　mediating　the　uptake　and　absorption　of　ammonium　ions　in　the　extracellular　space　of　the　cortical　circuit,　we　constructed　a　new　astrocyte　neuron　coupling　model,　which　is　composed　of　a　neuron　and　its　astrocytes　connected　through　the　extracellular　space,　taking　into　account　of　the　influence　of　extracellular　ammonium　ions.　The　numerical　results　verified　the　previous　experimental　observation　that　obtained　epileptic　firing　modes　of　neurons　and　postsynaptic　GABA　reversal　potential　depolarization　triggered　by　ammonia　injection.　In　addition,　we　also　determined　the　concentration-response　relationship　between　the　ammonium　ion　concentration　and　the　time　of　entering　epilepsy　and　predicted　the　threshold　of　the　ammonium　ion　concentration　for　the　onset　of　epilepsy.