This article presents the numerical investigation on the total ionizing dose (TID) radiation induced breakdown voltage shifting behavior of the silicon-on-insulator (SOI) buried P-pillar (BP) lateral double-diffused metal-oxide semiconductor (LDMOS) with a P-top region (TP). We validate the employed simulation models and structure parameters by the experiments of the 200 V rated SOI BP-LDMOS devices. We also discuss the breakdown voltage (BV) analysis of the SOI BPTP-LDMOS under different doping concentrations in the drift region. Because the lateral breakdown voltage can be effectively enhanced by the P-top region under STI layer, the SOI BPTP-LDMOS behaves a wider Nd window for rated 200 V compared with the SOI BP-LDMOS. Finally, we perform the numerical investigation of the TID radiation effect on the BV shift. Using the TID hardening design with the electric field modulation method, the hardened BPTP-LDMOS can achieve a significant improvement in the TID tolerance compared with the hardened SOI BP-LDMOS, from 575 to 775 krad(Si).