End-functional polystyrenes with the N,N-diethyldithiocarbamyl group were prepared by the photopolymerizations of styrene using alkyl diethyldithiocarbamylacetates as photoiniferters. Under UV light the end-functional polymers could initiate vinyl monomer to polymerize and form block copolymers, such as polystyrene-block-poly(methyl meth-acrylate), polystyrene-block-poly(vinyl acetate), and polystyrene-block-poly(n-butyl acrylate). According to end group analysis and EPR spectroscopy, AB-type block copolymers were produced. The glass transition temperatures and thermal stabilities of the block copolymers were investigated by means of thermal analysis.