Abstract: Abstract: The photosynthetic rate of morus australis poir is an important physical indicator of morus. The essay focuses on the analysis and discussion on the physical factor and the tiny meteorological phenomena factor, both of which exert effect on the photosynthetic rate of morus australis poir. With the help of an LI6400 portable photosynthetic determinator, the findings of a 24-hour close observation over the tiny meteorological phenomena factor during the mature period of morus australis poir are as follows: First, the correlativity between the leads degree of air hole and the photosynthetic rate and the transpiration rate of the blade is positive; second, the correlativity between the CO2 density of the morus australis poir and the leads degree of air hole is negative. The CO2 density exerts different effect on the leads degree of air hole at different stages, namely, the higher the density level is, the greater the effect will be; finally, among the tiny meteorological phenomena factors affecting the photosynthetic rate of morus australis poir, the correlativity between the illumination intensity as well as the blade temperature and the photosynthetic rate of morus australis poir blade is positive accordingly, and the photosynthetic rate decreases as the CO2 density of the morus australis poir increases. It is self-evident that the leads degree of air hole of morus australis poir is closely ralated to the photosynthetic rate of the blade and the CO2 density of the morus australis poir, in particular, more closely related to the transpiration rate; as important exterior factors, such meteorological phenomena factors as the illumination intensity, the CO2 density and the blade temperature have an great effect on the photosynthetic rate of the morus australis poir blade.