Abstract: Objective To establish a practical method of detecting cord plasma nonprotein bound iron(NPBI). M ethods Of 20 cord plasma samples,10 of mormal, 10 of asphyxial newborns, respectively, their NPBI were investigated by traditional and corrected blo emycin assay. Their standard curves, recovery rates and t-test statistical results were compared. Results We found the cord plasma NPBI were lower detected by tra ditional bleomycin assay in normal and asphyxial newborns, their recovery rate was only about 32%. There is an obviousely matrix effect. Though the NPBI of normal and asphyxial ne wborns had still significant difference by t-test,the NPBI values were so l ow th at it's easily disturbed and difficult to practice on clinical use. The detecte d results were improved by matrix effec-free bleomycin assay. Their rec overy rat es were reached about 101%and the NPBI values had statistical significant d iffe rence between normal and asphyxial newborn. Conclusion The matri x effec-free bleo mycin assay is a stable, real and better method to estimate the concentration of plasma NPBI practically on clinical use.