We have developed a simple physics-based two-dimensional analytical Off-state breakdown voltage model of a PBOSS Silicon-On-Insulator Lateral Diffused Metal Oxide Semiconductor (SOI-LDMOS) transistor. The analytical model includes the expressions of surface potential and electric field distributions in the drift region by solving the 2D Poisson’s equation. The electric field at the Si-SiO2 surface is modified by creating additional electric field peaks due to the presence of the PBOSS structure. The uniformly distributed electric field results in improving the breakdown voltage. Further, the breakdown voltage is analytically obtained via critical electric field concept to quantify the breakdown characteristic. The model exploits the impact of the critical device design parameters such as thickness and length of the PBOSS structure, doping, and thickness of the drift region on the surface electric field and the breakdown voltage. The proposed model is verified by the results obtained from ATLAS two dimensional simulations. The analytical model is of the high potential from a physical and mathematical point of view to design high voltage SOI-LDMOS transistors for power switching applications.