Bovine serum albumin/poly(acrylic acid), BSA/PAA, nano-scaled particles were produced by noncovalent bonds induced self-assembly method at acid pH area. Proper conditions during preparation process, such as pH value, BSA/PAA weight ratio(WR), PAA molecular weight, were researched by studying the hydrodynamic diameter, polydispersity index, and ? potential of the nanoparticles. Complex formation between BSA and PAA was studied by FT-IR, AFM, and TEM. BSA chains are supposed to be partly trapped in the nanoparticles core after interaction with PAA because of the electrostatic attractions and hydrogen bonds interactions between BSA and PAA, while the rest of the BSA chains should form the shell of the nanoparticles. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013