Through mRNA extract, RT and a series of PCR, phage antibody libraries were constructed from rP27(kip 1)-immunized and non-immunized mice. After only one round of selection with rP27(kip 1), clones from each library were chosen randomly and digested byTag I and Hinf I. 11 of 64 clones from the immunized animal had consistent restriction pattern, while none of the 64 clones from the non-immunized animal had, except that one had the same fragments pattern as that of the 11 clones. The 12 fragments were expressed inE. coli BL21(DE3)/pET-28b(+) system. ELISA showed that some of the fragments could bind to rP27(kip 1) specifically. AU these results implied that specific antibody can be obtained by genetic engineering without hybridoma or many rounds of growth and panning selection.