Bovine serum albumin nanoparticles(BSANP) were prepared by desolvation method. The activated folic acid (N-hydroxysuccinimide ester of folic acid) was conjuated to the surface of BSANP via the amino groups. Then the folate-conjugated BSANPs (folate-BSANP) were purified with Sephadex G-50 column and completely separated from unreacted folic acid. After chymotryptic hydrolysis, the extent of folate conjugation on the BSANP was determined by quantitative ultraviolet(UV) spectrophotometric analysis. It was found that the spectrum of trypsin digest of folate-conjugate BSANP is basically identical with that of folate, thus indicating folate is successfully expressed on the surface of BSANP. The folate-BSANP was averagely 66 nm in diameter and was spherical in shape. Folate-conjugated BSANP was achieved, which represents a potential new drug carrier for tumor cell-selective targeting.