In this article, high density polyethylene/clay nanocomposites were prepared via melt intercalation. The crystallization behavior was investigated uisng differential scanning calorimetry (DSC) at various cooling rates. Avrami, Ozawa, and Mo methods were applied to describe the crystallization process under nonisothermal conditions. The crystallization temperature, melting temperature, and crystallinity of nano-composites were found higher than those of neat PE-HD. The values of t_1/2, , and showed that clay played a role of heterogeneous nucleating agent and accelerated the crystallization process of PE-HD, which could be attributed to the "intercalation" structure formed between PE-HD and clay.