Abstract: Natural somatostatin,dextran-10 and tyramine are used to synthesis somatostatin-dextran-tyramine(SMS-Dx~(10)-tyramine,glycosylated somatostatin).The somatostatin receptor competition binding study of glycosylated somatostatin in vitro is carried out using rat brain cortex membranes(expressing somatostatin receptor type 2) and the radioligand of ~(125)I-Tyr~3-Octreotide.The radioiodinated glycosylated somatostatin is prepared by Iodogen method.The biodistribution and blood half life are investigated in normal rats.The glycosylated somatostatin posses high somatostatin type 2 receptor binding affinity,the same IC_(50)value as the reference ligand Octreotide,and the blood half-life is 6.7 h after post injection.The digestion and excretion is mainly through the hepatobiliary and kidney system.The adrenals gland has higher uptake,which is a somatostatin receptor positive organ.The radioiodinated glycosylated somatostatin shows promising properties and is worthy of further investigation.