Aim We used hedgehogs to study the effects of sialic acid in the structure of low density lipoprotein (LDL)and lipoprotein (a)[Lp(a)] on the metabolism of the LDL and Lp(a) with 125 iodine. Methods The end sialic acid on the stucture of LDL and lipoprotein (a) were removd with the treatment of neuraminidase.The desialylated lipoprotein (a) (ds-Lp (a), desialylated low density lipoprotein (ds-LDL),LDL and Lp (a)were marked with 125 iodine tyramine cellobiose. They were injected into the body of the hedge hogs via the armpil vein. The animals were put to death in 3 h and 6 h.The concentration of radioactivity in the blood, liver, spleen,kidney and gall were measured. The change of metabolism of ds-LDL and ds-Lp (a) were analyzed and compared with that of norma LDL and Lp (a). Results The experiments showed that the rate of the metabolism of ds-LDL in 3 h is 7.6% lower than that of LDL,and the rate of the metabolism of ds-LDL in 6 h is 12.23% higher than that of LDL. On the contrary the concentrations of ds-Lp (a) in all the organs reduced by 2 times and 3.85 times to the concentrations of Lp (a)in 3h and 6h respectively,LDL and ds-LDL canbe swallowed by the spleen cells and stored. Although Lp (a) can alsO be swallowed by the spleen cells,ds-LP (a) had a little to enter the spleen cells. Even so it can be removed quickly.Conclusions Experiments proved that sialic acid plays a very important role in the metabolism of Lp (a)and remaining stable of the structure of Lp (a).