The ruling Communist Party has pledged a wide range of economic reforms and the Washington-based institution said reducing the "unique and distorted role of the state" in banking and the wider financial sector was crucial.
"Wasteful investment, overindebtedness, and a weakly regulated shadow-banking system," had to be addressed for the broader agenda to succeed, it said.
The comments in the China Economic Update were unusually forthright for the World Bank.
"The state has formal ownership of 65 percent of commercial bank assets and de facto control of 95 percent of these assets, making it an outlier by international standards."
In some cases, it added, authorities were simultaneously owners, regulators and customers of banks.
China's financial system was still "unbalanced, repressed, costly to maintain, and potentially unstable", the bank said, repeating its description from a 2012 report.
"Failure to address these outcomes could deflect the economic trajectory after three decades of stellar performance."
In the document, the World Bank left its economic growth estimate for China this year at 7.1 per cent.
"Progress in rebalancing the sources of growth in domestic demand will remain incremental," it said.
China's leaders are trying to engineer a transformation of the country's growth model whereby consumer demand becomes the main driver rather than investment.
"China's financial system was developed to serve the old investment-driven growth model, effective during earlier phases but less so now," the World Bank said.
China itself has set a target of about 7.0 per cent growth in gross domestic product (GDP) for this year, though weak data during the first half of the year has led many private economists to expect that growth this year could come in below that figure.
