Group transfer polymerization of acrylonitrile was conducted in bulk at room temperature with 1,1,3-trimethyl-5-methylen-2, 6-dioxa-l1silacyclohexen (TMDSCH) as the initiator and tetrabutylammonium bibenzoate (TBABB) as the catalyst. The experimental results showed that the new GTP initiator gave polyacrylonitrile in fairly good yields with well control of the molecular weight and polydispersity.