Objective To study the variation of air particles with different vertical heights and provide theoretical basis for the construction and utilization of forest therapy.

Method  In this paper, the mass concentrations of TSP, PM₁₀, PM_2.5, and PM₁ at the height of human body (1.5 m), the middle of forest canopy (6 m), the canopy upper layer (12 m) of Cunninghamia lanceolata forest were observed for 24 hours in summer of 2017 with a cloudy weather in the Yandangshan of Wenzhou.

Result  1.The mass concentrations of different-sized particle matters varied in different heights. There was a significant difference between the TSP and PM_2.5, that of the middle of forest canopy were all the lowest in three heights. 2.The daily mean mass concentrations of TSP and PM₁₀ in the three heights were all reached the grad-Ⅱof national standard for urbanized area ambient air quality, and the concentrations of TSP in forest canopy reached the standard grade-Ⅰ. 3.During the observation period, the concentrations of particle matter in different heights were higher at night, and lower in the daytime. 4.The middle of canopy (H2) of air particulate matter in different vertical height was the lowest in the day time; there was no significant difference in TSP mass concentration in three heights, the mass concentrations of PM₁₀, PM_2.5 and PM₁ were generally low in human height at night. 5. The concentrations of four kinds of particles were significantly positively correlated with dew temperature and negatively correlated with air pressure. The correlation coefficient between PM_2.5 and both factors was the largest. The concentrations of PM₁₀, PM_2.5, and PM₁ were significantly positively correlated with temperature as well as maximum wind velocity, and negatively correlated with relative humidity. Every meteorological factor affected the mass concentration of air particles.

Conclusion  The middle of canopy is the best height for recreation in C. lanceolata forest in the Yandangshan of Wenzhou. It is most suitable for daytime travel.