This paper presents a vehicle design parameter screening, the first portion of our MDO efforts on occupant-centric vehicle design. The study uses a full simplified vehicle by considering occupant centric survivability performance under underbody mine blast loading. The top 10 design variables have been identified by TARDEC SMEs and analyzed systematically. 32 finite element models were built to represent fractional factorial combinations of these design parameters and used to determine the main contributors to vehicle structure response and occupant injury potentials. Four preferred design parameter selections have been found in this effort to achieve improved occupant survivability performance and structural response under underbody blast loadings. They are: optimized seat energy absorption system, higher standoff distance and vehicle mass, double-V underbody shape without structural reinforcement, and smaller vehicle width. The study found and confirmed that an optimized seat energy absorption system can lower occupant injury indices significantly. The efforts presented in this paper pave a road to a full system multidisciplinary design optimization.