Abstract: FAAS was applied to the determination of iron and manganese in trifolium and its extract. Working conditions of the atomic absorption spectrophotometer were studied and optimized. As shown by experimental results,no significant interferences were observed by the coexisting ions,Ca2+,Mg2+, Zn2+,Na+ and K+. The dry and powdered trifolium sample,was treated with conc. HNO3 in a crucible,evaporated to dryness and ignited in a muffle furnace at 500 ℃ for 1 h. Repeat the treatement and take up the ignited residue with 0.2 mol·L-1 HCl. The solution was used for FAAS determination. Linear relationships were obtained in the range of 0.50-4.00 mg·L-1 for Fe(Ⅲ) and 0.20-3.00 mg·L-1 for Mn(Ⅱ),with correlation coefficients of 0.999 6 and 0.999 0. As calculated from the slopes of the standard curves,the sensitivity obtained for iron was 0.028 mg·L-1/1% and for manganese was 0.011 mg·L-1/1%. Results obtained by test for recovery were 98.9% for iron,and 96.2% for manganese. In determination of the 2 elements in a trifolium sample for 5 times,values of RSD′s obtained were 2.45% for 67.0 μg·g-1 of iron,and 2.10% for 7.8 μg·g-1 of manganese.