To build up a programming code and solving it on computational numerical technique by developing energy balance equation for combine cycle power plant integrated with Trans-critical cycle. A computer programming code has been used to simulate a performance under various different conditions under different temperature and pressure circumstances and thermal performance on different cases of Brayton cycle have been analyzed using standard fluids. In this paper Brayton cycle, Rankine cycle and trans-critical cycle are combined which makes it tri-generate cycle and variations of temperature and pressure with thermal performance parameters such as thermal efficiency, exergy destructions in the various components using trans-critical cycle have been analyzed. It is observed that by increasing... condenser temperature of Rankine cycle, the combined cycle efficiency , net-work are increasing and by increasing the mass flow rate of Brayton cycle, combined cycle efficiency is decreasing while combined net-work is increasing. Similarly by increasing the exit pressure of pump in the trans-critical cycle, both the combined cycle efficiency & combined net work are decreasing also is decreasing and also by increasing the inlet temperature of turbine of trans-critical cycle, the combined cycle efficiency and combined net-work is increasing. By increasing the inlet pressure of pump of trans-critical cycle, combined cycle efficiency and combined net work (i.e. both) are increasing.