Pyramidal　neurons　in　the　electrosensory　lateral　line　lobe　(ELL)　of　weakly　electric　fish　activate　in　an　environment　of　time-varying　electric　fields,　which　are　generated　by　the　fish　itself,　while　how　these　pyramidal　neurons　would　behave　or　what　kinds　of　firing　patterns　these　neurons　would　produce　under　different　electric　fields　is　still　unclear.　In　this　research,　the　firing　behaviors　of　ELL　pyramidal　neuron　under　DC　and　AC　electric　field　stimulus　are　investigated　in　a　two-compartment　neuron　model.　By　means　of　numerical　simulations　we　show　that　firing　patterns　of　the　model　ELL　pyramidal　neuron　are　much　diverse　under　different　values　of　DC　electric　field,　and　neuronal　spike　frequency　exhibits　a　monotone　decreasing　trend　with　the　linearly　increased　DC　fields,　moreover,　the　transition　mode　between　these　firing　patterns　with　the　variation　of　DC　electric　fields　demonstrates　an　explicit　periodic　route.　While　for　AC　electric　fields,　neuronal　firing　frequency　periodically　transforms　with　the　increase　of　AC　frequency,　particularly,　a　special　transition　pattern　(from　multi-period　bursting　to　spiking)　repeatedly　appears　with　the　change　of　AC　frequency.　Our　simulation　results　indicate　that　ELL　pyramidal　neurons　fire　dynamically　under　the　time-varying　electric　fields,　the　diversity　of　firing　patterns　and　their　periodic　transition　modes　may　imply　the　potential　roles　of　these　dynamical　firings　in　the　coding　strategy　of　sensory　information　processing.