The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been\nhigh lightened in recent years and have become an increasingly important subject for ship designers and\nowners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2 emissions\nfrom ships, and their proposed Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational\nIndicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be\nemployed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions.\nIn this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main\npropulsion machinery is introduced and three possible types of Waste Heat Recovery Systems(WHRS) are\ndesigned. To calculate the Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational\nIndicator (EEOI) of the given large container ship, two software packages are developed. Impact of\nperformance of Waste Heat Recovery Systems(WHRS), as well as different ship design parameters, have been\nvaried to see influence of these parameters on the EEDI. From the viewpoint of operation and maintenance,\nlowering the ship speed and improve container load rate can greatly reduce Energy Efficiency Operational\nIndicator (EEOI) and further reduce total fuel consumption. Although the large container ship itself can reach\nthe International Maritime Organization requirements of EEDI at the first stage, i.e. with a reduction factor\n10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI\nreduction factor to 20% under the reference line value.