Turbine efficiency is a measure of turbine perfomance to produce a power in comparison of power generated by the turbine engine and the turbine performance. Some factors that influence turbine efficiency are the debit of water flowing, water density, earth gravity acceleration, and the height of water falling (head). The research was conducted in PLTA Wonogiri and the data was taken according to the situation in the field, such as operating unit, power generated, water debit, kWh (power) production, voltagetransformer, temperature transformer, reservoir elevation, intake elevation, H delta, tailrace elevation, spill way or hollow jet, and the amount of diesel fuel. The highest average value of turbine engine efficiency of unit 1 was on July 2017, which is 92.5%. Furthermore, the highest efficiency of turbine engine in unit 2 was recorded on April 2017, which is 90.9%. In terms of the lowest efficiency, it occured on January 2017 with 72.4% efficiency and on November 2017 with 68.1% efficiency, respectively for unit 1 and 2. The total average value of turbine engine efficiency in January to December 2017 for unit 1 is 83.3 % and unit 2 is 84.8 %.