This study aims to determined the impact of the moving blade breakdown on turbine performance of steam turbine at PT. Indocement Tarjun Plant 12 by comparing the results of data obtained during from performance test in 1999, 2017, 2018, and 2019. This research data is taken from the control room of PT. Indocement Tarjun, variable data obtained in the form of load, main inlet steam temperature, main inlet steam pressure, HP heater feed outlet temperature, HP heater feed outlet pressure, main steam flow, and turbine by pass flow. The data is processed to get the turbine heat rate and the efficiency per time of each performance test and then averaging the data results over time, then comparing the turbine heat rate and the average efficiency when the turbine at normal condition and abnorma condition. The calculation of turbine heat rate using heat & mass balance method, turbine efficiency is obtained by comparing the energy of 1 kW with turbine heat rate and multiplying 100%. The result of the average heat turbine calculation per performance test is August 1999 is 2.546, June 2017 2,56, May 2018 2.67, and January-March 2019 4.24. The average value of turbine efficiency in August 1999was39.30%,June201739.07%,May201839.46%,January-March201923.99%.Turbine power plant performance of PT Indocement Tarjun Plant 12 decreased from 1999 to 2019 by 13,47%.