We　show　the　connection　between　the　second　Chern　number　and　topological　defects,　in　a　(4+1)　-dimensional　time　-reversal　invariant　Dirac　lattice　model.　It　is　discovered　that　two　types　of　topological　defects,　the　five　-dimensional　(5D)　and　four-dimensional　(4D)　point　defects　arise　from　the　singular　points　of　wave　functions　together　with　the　geometric　meaning　of　the　second　Chern　number.　We　demonstrated　that　the　5D　point　defects　appear　at　the　band　crossing　positions　with　a　topological　transition,　leading　to　a　jump　of　the　second　Chern　number.　The　4D　point　defects　exist　in　an　insulating　bulk,　whose　topological　charges　can　give　the　evaluations　of　the　second　Chern　number　of　energy　bands.　Finally,　we　discussed　the　possible　structures　of　the　boundary　states　in　the　light　of　the　realization　way　of　the　4D　model.　Our　theory　provides　not　only　a　new　perspective　to　grasp　the　second　Chern　number,　but　also　a　simple　approach　to　derive　its　values　without　calculating　any　integrals.