In this paper, the total ionizing dose (TID) response of body-on-insulator (BOI) FinFETs is investigated and compared with bulk Si FinFETs by 3D TCAD simulation. The irradiation induced off-state leakage current (I off ) is significantly reduced by the localized oxide layer in the sub-fin region of BOI FinFETs. The I off of BOI FinFETs increases negligibly after irradiation. In contrast, the I off of bulk Si FinFETs with the same geometry increases by several times after irradiation. Besides, BOI FinFETs show weaker dependence on fin width, and the off-state leakage current of bulk FinFETs induced by TID irradiation increases significantly with the decrease of fin width. Moreover, with the scaling of gate length, the I off of BOI FinFETs remains almost unchanged, while it increases by more than an order of magnitude for bulk FinFETs, which indicates that BOI FinFETs show strong scaling capability in terms of TID. Therefore, BOI FinFETs demonstrate strong TID tolerance and scaling capability, and have great potential for application in radiation environment.