Abstarct: A steam turbine is a type of prime mover used in a trigeneration system. A steam turbine is used of generating electrical power by converting steam energy into mechanical energy. This study performs the estimation of percentages of emission reductions, economic analysis and technical evaluations for a combined cooling heating and power (CCHP) or trigeneration with Rankine cycle which natural gas has been used as fuel. This trigeneration system includes a boiler, a steam turbine, a heat exchanger, a single effect absorption chiller and pump. Some specific parameters in this study are considered including the electrical efficiency, efficiency of cogeneration of electricity and cooling, efficiency of cogeneration of electricity and heating and trigeneration system efficiency, as well as exergy efficiency. Various output and environmental performance parameters such as percentage reduction in operating costs, percentage of fuel consumption reduction, percentage of emission reductions and economic and technical discussions under the influence of different temperatures and pressures of steam turbine input are investigated. Also, the performance of absorption chiller and trigeneration system under different operating conditions have been investigated. This study shows that the use of the Trigeneration system results in an increase of 23.75% in Trigeneration CO2 Emission Reduction (T〖CO〗_2ER) and 15.86% in Trigeneration Primary Energy Saving (TPES) and 33.14% in Operational Cost Reduction (CR) to conventional systems. There is considerable progress when using a Trigeneration system. The efficiency of the Trigeneration system will be 82.64%. Optimization of total annual costs has also been done with of steam turbine input temperature and pressure،Isentropic efficiency and Heat Exchanger Efficiency decision variables.