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 (R) 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.