The exergy and exergoeconomic of the Qazvin steam power plant carried out here. In this paper the exergy destruction and efficiency of each component of this power plant is estimated. Since in every power plant there are different working loads and ambient temperature is varying during seasons, the effect of the load variations and the ambient temperature on the exergy analysis of power plant are calculated in order to obtain a good insight into this analysis. According the results, the boiler has the highest exergy destruction rate. The variation of the ambient temperature, is at the range 5ºc to 30ºc. Increasing the ambient temperature, the exergy destruction rate of all components increased. Increasing load of the power plant from 125 MW to 263 MW increases exergy efficiency of boiler and turbine. Then exergoeconomic analysis is done. The results show that the boiler has the highest cost of exergy destruction. Economic factors including the relative cost difference (rk) and exergoeconomic factor (fk), are calculated for each component. According to the results, the boiler, the low pressure turbine and the condenser of Qazvin power plant, are major exergy destructors respectively.