Abstract: A comparative study on the photosynthetic characteristics of Plagiomnium acuium (Lindb.)T.Kop., P.maximoviozii (Lindb.)T.Kp.,two overwintering host mosses for Chinese gall aphid(Schlechtendalia chinensis),was conducted by using CI-301PS in Summer, Winter.The results showed that the photosynthetic capacity of these two mosses species was 125.67, 94.63μmol CO₂·kg^-1 DW·s^-1 in Summer,and 58.1, 62.1μmol CO₂·kg^-1 DW·s^-1 in Winter,respectively.The dark respiration rates of these two species in Summer significantly exceeded those in Winter.The light complementary point of these two mosses species was in the range from 20 to 40μmol·m^-2·s^-1 ,and light saturated point was from 200 to 400μmol·m^-2·s^-1 ,with higher value in Summer, lower value in Winter.Their apparent quantum yields were 1.535, 1.559 in Summer,but only 0.456, 0.459 in Winter.The optimum temperature for photosynthesis of these two mosses species was 20 to 35℃,also higher in Summer, lower in Winter.No matter which species, growing season,the temperature coefficients(Q₁₀) measured in the range of 0～20℃ were similar,ranging from 1.15 to 1.23.These two moss species could maintain a certain net photosynthesis for 10～30 minutes under temperature stress from -15 to -10℃, from 40 to 45℃.