Reliability of turbine plants has not been investigated since 1980's because turbine plants have not been installed due to more fuel consumption than those of diesel plants. However steam turbine ships are gradually increasing since the LNG vessels began to be constructed. This report investigates alarm and failure situations of turbine ships based on data gathered by “Committee on Ship Reliability Investigation (CSRI) ” and actual field data of LNG turbine ships compared with reliability data of diesel ships on same period. Also this report refers to future design of turbine plant for reliability improvement. Among analysis results of the turbine and diesel plant reliability, authors picked up some problems which increase Failure Rate or Manning Index.1) Major trouble of auxiliary equipment were caused by low grade fuel. The equipment which is most affected is the fuel purifier.2) Automatic equipment failures occurred every 18 days and needed 8.5 MH. MI and FR of those failures occupied approximately 1/3 of whole plant. About 50 to 70% of reasons are judged to be ghost or the unknown.3) Maintenance works of turbine plant required much time for preparation works like cooling down of steam line, transfer of big mass or valve operation of complex piping system.