The changes of O-J-I-P transients were investigated using leaves of four subtropical plant species (Crinum asiaticum var. japonicum, Osmanthus insularis, Chloranthus glaber and Asplenium antiquum) under the natural conditions in winter, in order to select the stress indicators for diagnosing physiological states of plants under low temperature. In the O-J-I-P transients of these species, the fluorescence intensity was found to be higher in O-step and lower in P-step in winter than in summer. Particularly, the fluorescence intensity of the P-step in Crinum asiaticum var. japonicum was lower than those of other three plant species, indicating that Crinum asiaticum var. japonicum is the most sensitive to low temperature. Of the chlorophyll fluorescence parameters derived from O-J-I-P transients of four subtropical plants, Fm, Fv/Fo, ABS/CS, TRo/CS, $phi_{po}$ and $phi_{po}/(1-phi_{po})$ decreased significantly with the increase of Fo, Sm, N, EToICS, ETo/RC and $psi_o/(1-psi_o)$ depending on temperature drop in winter. Therefore, these parameters could be used as indicators for estimating low temperature stress and diagnosing physiological states of plants under the natural conditions in winter.