The purpose of this study is to predict outlet temperature and humidity through underground pit for the reduction of cooling load and heating load. Commonly, the underground temperature is lower than outdoor in summer but the reverse happens in winter. When the outdoor average air temperature is $25.7^{circ}C$ during cooling periods, the average outlet air temperature through underground pit is $23.6^{circ}C$ with 3 m-depth and 60m-length and is $22.2^{circ}C$ with 3 m-depth and 150 m-length. When the outdoor average air temperature is $4.9^{circ}C$ during heating periods, the average outlet air temperature through underground pit is $7.7^{circ}C$ with 3m-depth and 60 m-length and is $10.8^{circ}C$ with 3 m-depth and 150 m-length. The outlet air temperature is affected by more length than depth of underground pit. The diffusion ratio of outdoor humidity is $-7.7 imes10^{-8}kg/s$ in cooling periods and $9.29 imes10^{-7}kg/s$ in heating periods.