This work demonstrates the feasibility of composite thin film containing nano-scale recording particles to high-density optical data storage. For an HD-DVD format "nano"-optical disk containing such a nano-composite layer, modulation higher than 0.5 was achieved when 11T and 4T signals were respectively written into the disk by using a blue-laser dynamic tester. Transmission electron microscopy (TEM) characterization attributed the recording mechanism to the grain coalescence/coarsening and crystallinity change of nano-recording particles which, in turn, results in sufficient reflectivity difference for signal readout. The utilization of nano-composite recording layers may drastically simplify the optical disk structure and thus is a promising alternative for next-generation write-once data recording.