The reverse micellar system of Triton X-100/pentanol/cyclohexane was used to imitate native thylakoid membrane and study the energy transfer from C-phycocyanin (C-PC) to chlorophyll a. C-PC is completely solubilized in water and stable due to the protection of the water layer. When chlorophyll a is added into the system, the chlorophyll a molecules locate in the hydrophillic region. Energy transfer from C-PC to chlorophyll a takes place with much lower efficiency than in native cells. The efficiency of energy transfer increases with the concentration of chlorophyll a while it decreases with the increase of the molar ratio (R w ) of water to Triton X-100. When the concentration of chlorophyll a is 4.2 10 - 7 M and that of C-PC is 1.2 10 - 7 M in the reverse micelles with R w values of 2.5 and 7.5, the efficiencies of energy transfer are only 33 and 13%, respectively. The reason of the low efficiencies of energy transfer may be that the energy donor and acceptor are not coupled so well as in the native cells in which allophycocyanin (APC) plays a role of the bridge for energy transfer.