This study explores environmental factors affecting phytoncides, negative air ions (NAIs) concentrations, and the human comfort index (HCI) compared and analyzed across different sampling sites and seasons to provide planning guidance for management. The research was conducted at the Lienhuachih Research Center in central Taiwan. Findings from the research revealed that the human comfort level at the Lienhuachih Research Center was relatively high in spring, summer, and fall, with the highest level observed in fall. Concentrations of phytoncides and NAIs varied with the seasons, with summer and fall recording the highest levels. The main constituents were limonene, linalool and terpinen-4-ol. The study found significant correlation between relative humidity and NAIs concentrations, with temperature being key to the thermal human comfort index though variations in the composition and concentration of phytoncides were detected at different sites. In conclusion, we recommend taking into consideration the characteristics of seasons and locations in planning optimal healing activities for forest therapy.