The reduction of air pollutants, such as green house gas,NOx and SOx,is required in recent years. Regulation against emission gas from vessels has been also strengthened sequentially in conformity with the MARPOL73/78 ANNEX VI. Under such conditions,the superiority of natural gas attracts attention,and an early introduction of LNG-fueled ships is expected. Safety standard for LNG-fueled ship and its required equipment are now discussed in IMO and ISO,but unfortunately,the discussion does not refer to any safety evaluation method for the transfer of LNG fuel between vessels.In the previous year, the Ministry of Land,Infrastructure, Transport and Tourism started a project for early introduction of LNG-fueled ship, and published a safety manual and operative guidelines on LNG transfer.In that project, we took charge of safety evaluation of Ship-to-Ship transfer of LNG fuel using a flexible hose.In order to prepare operative guidelines on LNG transfer between a bunker ship and a LNG-fueled ship,we have proposed anew safety evaluation process. Following the process, we have examined the limiting environmental conditions of LNG transfer based on the results of numerical calculations of motions of two moored vessels and the LNG transfer hose, respectively. This paper presents the results of the above-mentioned safety evaluation.