The compatibilities of polysulfone (B)-nylon 6(N) block copolymers with the ble-nd．of homopolysulfone and homonylon 6 and the properties of the block capolymers and their．blends in various solvents were studied．The phenomenon that different viscosities and molecular conformation when the copolymers were dissolved in O-chlorophenol and in formic acid were observed．The B-N (or N-B-N) block copolymers can play a role of the emulsifier in these solvents pai-rs：formic acid-chloroform．formic acid-chlorobenzene and formic acid-dichlorometha-ne．Stabilities of these emulsions depend on composition of copolymers (as emulsifiers) and the ratios of volume of these solvents pairs in each system．The presence of two phase in the B-N (or N-B-N) block copolymers were characterized by PM and SEM．The results show that B-N (or N-B-N) block copolymers can be a compatible agent for polymer-polymer systems and solvent—solvent systems．