Abstract: On the basis of investigating natural vegetation of Taiwan pine(Pinus taiwanensis) forest, four Taiwan pine seedling plots with transmissivities of 100%, 45%, 37% and 16% were established to measure regularly the photosynthetic ratio, respiratory ratio, evapotranspiration ratio, increments of organs and biomass. The results showed that:(1) Illumination had significant influence on the growth and physiological process of P. taiwanensis. The seedling with transmissivitiy of 100% was the strongest. There exists a close relationship between photosynthetic effective radiation and photosynthetic effectiveness, which follows the equation of Y=19.510 8X0.0282 .(2) The P. taiwanensis seedlings had the characteristics of low water potential, high photo compensation point(5.26 W·m-2), high water utilization ratio(3.01×10-3), deep rooting and strong drought tolerance. It is proved that this species is suitable to be planted as water conservation forest in mountainous area of subtropic region.