The　frequency　diverse　array　(FDA)　can　generate　a　range-angle-coupled　beampattern　by　introducing　an　additional　frequency　shift　to　its　array　element.　The　FDA　has　gained　more　and　more　attention　due　to　its　superiority　over　traditional　phased　array.　However,　different　from　phased　arrays,　frequency　offset　exists　in　the　FDA　as　a　unique　parameter,　its　error　will　unavoidably　affect　the　performance　of　the　array,　but　current　publications　barely　investigate　into　it.　In　this　article,　an　approach　based　on　interval　analysis　is　proposed　to　analyze　the　tolerance　of　the　power　pattern,　which　is　caused　by　the　deviation　of　frequency　offset　in　the　manufacturing　process.　Numerical　simulations　are　implemented　to　validate　the　proposed　method　and　point　out　its　characteristics　and　potential.