Alain Perrin's side are aiming to win the competition for the first time and displayed their quality in a straightforward success in Sydney.
Oman took the lead in the 18th minute of the clash that was held behind closed doors, but the two-time Asian Cup runners-up roared back to claim victory.
Shandong Luneng midfielder Hao Junmin was among the scorers for China as they extended their unbeaten run to 10 games.
China begin their quest for the title with a game against Group B rivals Saudi Arabia, who they lost to in the 1984 final, on Saturday.
Oman - who have been drawn in Group A - meet two-time winners South Korea in their opening encounter.
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