Thermoelectric Air Conditioner (TEAC) has gained increasing attention in recent years and has started to become a new design direction for large cooling capacity scenarios. This paper presents the investigation of temperature and humidity in air-to-air TEAC with large cooling capacity. The simulation model of thermoelectric cooling unit has been established to analyze the impact of temperature and humidity on the cooling performance. The results show that the impact of temperature on the cooling performance is linear, with an average increase of 32.6 W in Q(c) for every 2 degrees C increases in indoor temperature, and an average decrease of 23.0 W in Q(c) for every 2 degrees C increases in outdoor temperature. Moreover, the sensitivity of the cold-side outlet air temperature to indoor temperature is 5.7 times higher than the sensitivity to outdoor temperature. In contrast, the influence of humidity on cooling performance is nonlinear and complex. When humidity is low, the cooling performance is hardly affected. However, when humidity increases from 40 % to 60 %, due to the air condensation process, the cooling performance improves significantly, with an average increase of 50.8 W in Q(c). Also, the sensitivity of the outlet air temperature to high humidity air is significantly higher than that to low humidity air. Under various working conditions, by adjusting the current, the outlet air temperature of the TEAC can be maintained at 16 degrees C-20 degrees C, all of which meet the thermal comfort standard. Furthermore, the Q(c) of the system can reach similar to 2500 W under rated working condition and the COP is as high as 2.397 under low temperature condition. This study analyzes the heat and mass transfer and investigates the practicality of TEAC in a variety of complex and changing scenarios, providing a vital reference for the broader application of thermoelectric cooling technology.