The　uncertainties　of　multigroup　cross　sections　notably　impact　eigenvalue　of　neutron-transport　equation.　We　report　on　a　total　sensitivity　analysis　and　total　uncertainty　analysis　code　named　UNICORN　that　has　been　developed　by　applying　the　direct　numerical　perturbation　method　and　statistical　sampling　method.　In　order　to　consider　the　contributions　of　various　basic　cross　sections　and　the　implicit　effects　which　are　indirect　results　of　multigroup　cross　sections　through　resonance　self-shielding　calculation,　an　improved　multigroup　cross-section　perturbation　model　is　developed.　The　DRAGON　4.0　code,　with　application　of　WIMSD-4　format　library,　is　used　by　UNICORN　to　carry　out　the　resonance　self-shielding　and　neutron-transport　calculations.　In　addition,　the　bootstrap　technique　has　been　applied　to　the　statistical　sampling　method　in　UNICORN　to　obtain　much　steadier　and　more　reliable　uncertainty　results.　The　UNICORN　code　has　been　verified　against　TSUNAMI-1D　by　analyzing　the　case　of　TMI-1　pin-cell.　The　numerical　results　show　that　the　total　uncertainty　of　eigenvalue　caused　by　cross　sections　can　reach　up　to　be　about　0.72%.　Therefore　the　contributions　of　the　basic　cross　sections　and　their　implicit　effects　are　not　negligible.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.