Solar UV radiation in aquatic environments is known to cause a variety of effects on phytoplankton.However,to what extent such impacts would depend on temperature has hardly documented.During the winter (October 15 to November 16) 2005,we carried out simulated in situ experiments to determine the effects of solar UV radiation (UVR,280-400 nm) in a relation to temperature on primary productivity of natural phytoplankton assemblages in a coastal site (23° 24’ N,117° 07’ E) of the Southern China Sea.Surface seawater samples were collected and dispensed into quartz tubes,inoculated with radiocarbon and then exposed to solar radiation for 3 hours to determine photosynthetic rates under 3 quality radiation treatments (i.e.PAB,280-700 nm; PA,320-700 nm and P,400-700 nm) using different UV cut-off filters.