Abstract: The purification and character of spectrum of red protein(Rx) of Nostoc flagelliforme was studied in the paper.First,the cell of Nostoc flagelliforme was broken up with ultrasonic treatment,then the phycobiliprotein was preliminary purified with salting out and purified by chromatography with DEAE-DE52 as a medium.The fluorescence spectra were detected at room temperature and liquid nitrogen condition.The absorption peak of Rx was at 520 nm,the peak of fluorescence emission at room temperature and liquid nitrogen temperature were at 625 and 630 nm respectively,the peak of fluorescence excitation at room temperature and liquid nitrogen temperature were at 615 and 610 nm respectively,the rising time of fluorescence and life time were 495,2 200 picosecond respectively.With the results above,it could be concluded that the energy absorbed by Rx could transfer to PC then via PC to APC,and could also transfer to APC directly.