The navy should "accelerate its transformation and modernisation in a sturdy way, and make extended preparations for military combat in order to make greater contributions to safeguard national security," he said.
Addressing the powerful Central Military Commission, Hu said: "Our work must closely encircle the main theme of national defence and military building."
His comments, which were posted in a statement on a government website, come as the United States and Beijing's neighbours have expressed concerns over its naval ambitions, particularly in the South China Sea.
Several Asian nations have competing claims over parts of the South China Sea, believed to encompass huge oil and gas reserves, while China claims it all. One-third of global seaborne trade passes through the region.
Vietnam and the Philippines have accused Chinese forces of increasing aggression there.