Abstract: With the development of technology, effective countermeasures of decoy launcher are developed. Decoy Launcher Defence System (DLDS) designed to detect, to track and to localize the incoming Decoy from the enemies and it is a countermeasure system. The system offers a complete solution to detect and locate an incoming Decoy and provides highly effective defence for the system. The DLDS shall enable timely defence against incoming Decoys at sufficient range from the submarine to guarantee safety and survivability of own platform. Controlling of decoy launcher plays a crucial role in launching and firing of Decoys. For controlling the Decoy Launcher, two control units are there. They are Electronic Control Unit (ECU) and Remote Unit (RU). ECU is manually controlled and it act as master controller for the launcher. RU is controlled by directors through remotely (infrared signals). It is necessary to improve the reliability for the control units. In order to obtain the reliability of ECU and RU of DLDS, in this paper developed the Reliability Prediction, Reliability Block Diagram (RBD) and Failure Mode Effect and Criticality analysis (FMECA). Reliability Analysis gives the Prediction of the failure Rate and Mean Time Between Failures (MTBF). Reliability Prediction obtained in accordance with MIL-HDBK-217F2. Reliability Block Diagram (RBD) used to know the parts reliability how it contributes to success or failure of a system using logical operations of the system. FMECA used to obtain the failure modes of the components, their effect on system, identifies the criticality and corresponding changes are made in the design to reduce the failure modes. The procedure for performing a failure mode effects and criticality analysis developed by MIL-STD-1629. To control these failures proper methods are considered to improve the reliability of system. The reliability analysis is carried out using ITEMSOFT Tool.