Abstract: In order to understand the effect of different green biomass in communities on regulating thermal comfort. The green biomass and physiological equivalent temperature PET values of 20 quadrats of arbor-shrub-grass community in Minjiang Park（south）of Fuzhou were calculated. And the correlation between green quantity and PET values was analyzed. The results showed that in the arbor-shrub-grass community, when the total green biomass per 100 m² was less than 800 m³, the greater the green biomass was, the better the effect of community on regulating thermal comfort was. When the total green biomass per 100 m² was greater than 800 m³, the change of green biomass did not affect the thermal comfort. When the proportion of tree green reached 0.9, the community had the best effect on improving thermal comfort.