Abstract: The foreign genes have expressed in cyanobacteria, since the moleculor biology and gene engineering have developed.This make it possible to analyze the effects of foreign gene on the photosynthesis of cyanobacteria cells.Three types of cells, wild type cells of Anabaena sp.PCC 7120, and its transgenic cells To1 and To2, which came from two different transforming systems, were used in this work.It showed that the growth rates of transgenic cells were smaller than thoste of the wild type.The saturation light intensity of transgenic cells was 480μEm-2s-1 which was similar to that of wild type cells, The maximum oxygen evolution rate was about 360umolO2/mg Chl·hr.The absorption spectra showed that all of them had the chl a, carotenoid and phycocyanin.The phycocyanin content in one type of transgenic cells (To2) was much higher than that of wild types cell and To1.The low temperature fluorescence emission spectra results displayed that the energy transfer from phycob-iliprotein to photosystem I in transgenic cells was decreased, and the effects were also different in two types of transgenic cells.