Second law and sensitivity analysis of a lignite-fired Thermal Power Plant (TPP) are implemented by using the data obtained from a simulated 245 MWel TPP in Thermoflex simulation software. In this regard, exergy destruction and exergy efficiency of each component of the power plant and power generation, emissions and exergetic performance of the overall TPP is determined. Also sensitivity analysis is carried out by changing some essential parameters. In addition, power plant is fired with 9 other types of Turkish lignites. From exergy efficiency and emissions perspectives, it can be stated that, for the same power generation capacity, Soma lignite can be considered as the best lignite type among others. Moreover, for low grade Turkish lignites, two certain coefficients have been determined, in order to calculate directly the approximate fuels chemical exergies with the help of Lower Heating Value (LHV) and Higher Heating Value (HHV) of the lignites.