The purpose of this paper is to establish a maintenance program for the sea water System as a critical part from Desalination Unit type (MED/TCD), to satisfy all requirements needed as the main supplier for most of the systems in the desalination unit, improve the performance of desalination unit, and increase the life time of its components. The methodology/approach – by applying the scientific method (four step method) plus the PDCA cycle, it means we apply the Six Sigma philosophy. To improve the performance of the multi effects Desalination unit and increase the operational lifetime, we will work on one of the critical system in the MED/TCD unit (Sea Water System SWS) establishing maintenance program using the Six Sigma philosophy, define, measure, analyze, improve, and control (DMAIC) method for problem-solving methodology in MED/TCD Unit, to increase the Reliability and Availability of the MED/TCD Unit and increase the unit lifetime. Keywords: Six Sigma, Multi Effect Desalination, Sea Water System, Reliability Centered Maintenance, Plan-Do-Check-Act Cycle, Reliability, Availability. Abbreviations:- SWS                Sea Water System. PDCA             plan – Do – Check – Act Cycle. MED               Multi Effect Desalination. MED/TCD       Multi Effect Desalination/ Thermo-compression Desalination. DMAIC           Define – Measure – Analysis – Improve – Control Cycle. RCM               Reliability Centered Maintenance. PMP                Preventive Maintenance Program. IMS                 Integrated Management System. DPMO             Defects Per Million Opportunity. DOE                 Design Of Experiment . DFSS                Design For Six Sigma. PHE                  Plate Heat Exchanger. SIPOC              Supplier, Inputs, Process, Outputs, and Customers . CTQ                  Critical To Quality. ANOVA           Analysis Of Varience. DPU                 Defects Per Unit. RCMP              Reliability Centered Maintenance Program.