Oil and gas exploration of large reservoirs in deep water has accelerated the need to explore structures suitable for these depths, which operate more economically in deep water. A Spar platform is one such compliant offshore floating structure used for deep water applications for the drilling, production, processing, storage and offloading of ocean deposits. The Spar is modeled as a rigid body with 6 degrees-of-freedom, connected to the sea floor by multicomponent catenary mooring lines, which are attached to the Spar at the fairleads. The response-dependent stiffness matrix consists of three parts: (a) the hydrostatics provide restoring force in heave, roll and pitch; (b) the mooring lines provide the restoring force which are represented here by nonlinear horizontal; and (c) vertical springs. An unidirectional regular wave model is used for computing the incident wave kinematics by Airy's wave theory and force by Morison's equation. The response analysis is performed in time domain to solve the dynamic behavior of a moored Spar platform as an integrated system using the iterative incremental Newmark's Beta approach. Numerical studies are conducted for several regular waves.