Abstract: In this paper, the UV, IR and NMR spectral characteristics of the antitumor antibiotic 1588 are reported. Besides, it was also resolved on a CM-Sephadex C-25 column with a concentration gradient of ammonium formate into 15 components. Furthermore, the physicochemical and biological properties of the two main components, 1588-74-3 and 1588-74-9 (amounting to 23.4% and 11.3%, respectively), were studied.The paper and thin-layer chromatograms of the acid hydrolysate of these two main components were different from those of bleomycin A₂ and A₅. In addition, these two main components of antibiotic 1588 were also found to be different from other members of the phleomycin-bleomycin group in their UV absorption ratios, pH stabilities and the behavior of chromatography. So, antibiotic 1588 might be considered as a new member of this group.