The increase in inlet air temperature significantly reduces the efficiency of gas-steam combined cycle (GSCC) system, a problem that becomes particularly pronounced in high-temperature environment. Selecting an appropriate inlet air cooling (IAC) technology is of great importance for enhancing system performance. In order to comprehensive reveal the characteristics of the IAC technology, this study establishes an environmental thermoeconomic cost (ETC) model to investigate the impact of two IAC technologies, including absorption refrigeration cooling (ARC) and spray evaporative cooling (SEC), on the performance of a GSCC from three aspects of energy, economy, and environment (3E). The results show that the IAC technology can effectively reduce the impact of ambient temperature on the system environmental thermoeconomic performance. For the ARC technology, the cooling effectiveness improves with increasing ambient temperature, leading to a maximum ETC reduction of 3.6%. For the SEC technology, the cooling effectiveness is more significantly affected by relative humidity (RH) as ambient temperature increases, with a maximum cost reduction of 0.64% for every 10% decrease in RH. Under arid climate conditions, the SEC technology demonstrates superior performance in terms of cost-effectiveness and environmental impact. Conversely, in high-humidity environment, the ARC technology provides the greatest enhancement in GSCC performance. This research provides scientific support for selecting cooling methods under different environmental conditions, and offers practical significance for optimizing the GSCC operational performance.