A well-defined method for discovering an easy and effective strategy through graft copolymer derived from poly (methylmethacrylate) (PMMA) as a monomer, high-density polyethylene (HDPE) and its organoclay nanocomposite with physicochemical and mechanical properties was successfully prepared by reversible addition-fragmentation transfer (RAFT) polymerization, and factors organoclay (Cloisite® 20 A) on the terminal features of the obtained graft copolymer were investigated. First, maleic anhydride (MA) was grafted onto HDPE directed by, the inauguration of an anhydride chain with ethanolamine to develop a hydroxylated high-density polyethylene (HDPE-OH). After that, the hydroxyl masses were esterified by using RAFT agent, 4-cyano-4-[(phenyl carbon thionyl) sulfanyl valeric acid to obtain HDPE-CTA macroinitiator. Then, the MMA monomer was grafted onto HDPE via the RAFT method to obtain the HDPE-g-PMMA graft copolymer. In the end, HDPE-g-PMMA/clay nanocomposite by a solution intercalation method was synthesized. The structures of the, copolymer and nanocomposite were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and Transmission electron microscopy (TEM) techniques. It explores for the synthesis of HDPE-g-PMMA/clay nanocomposites, disclosed a foliated structure. Based on the thermic behavior, synthesized HDPE-g-PMMA/clay nanocomposites can display the above thermic solidity with just some extent (5) of organoclay.