The performance of door assembly is very significant for the vehicle design and door sag/set is one of the important attribute for design of door assembly.This paper provides an overview of conventional approach for door sag/set study based on door-hinge-BIW assembly (system level approach) and its limitation over new approach based on subassembly (subsystem level approach).The door sag/set simulation at system level is the most common approach adopted across auto industry. This approach evaluates only structural adequacy of door assembly system for sag load. To find key contributor for door sagging is always been time consuming task with conventional approach thus there is a delay in providing design enablers to meet the design target.New approach of door sag/set at “subsystem level” evaluates the structural stiffness contribution of individual subsystem. It support for setting up the target at subsystem level, which integrate and regulate the system level performance. This approach is also useful for generating the design enablers and for optimization of door-hinge-BIW assembly with higher reliability.The commercial software “ABAQUS STANDARD” is used as FE solver to simulate the door sag/set by both the approaches with application of material, geometrical and contact nonlinearities.