A novel protein with anti-tumor activities named malanin was isolated and purified from an endemic plant in Yunnan and Guangxi provinces. Effects of copper ion, silver ion and calcium ion on malanin and apo-malanin fluorescence spectra were studied. The results showed that copper ion leads to obvious statistic quenching of malanin and apo-malanin fluorescence. The dissociation constant of them from malanin and apo-malanin were about 2.37 X 10(-4) and 2.66 X 10(-4) mol · L(-1), respectively. The silver ion did not have quenching action on malanin fluorescence, but it had statistic quenching effect on apo-malanin fluorescence, and its dissociation constant was 2.37 X 10(-4) mol · L(-1). Calcium ion did not have quenching action on malanin and apo-malanin fluorescence. It plays an important role in keeping malanin natural conformation.