The“Corporate Governance Guidelines for Listed Companies”，issued in 2002，requires that the companies with controlling shareholder stake of more than 30% should adopt a cumulative voting system in the election of directors，and that this system should be written into the articles of association． Is this mandatory requirement effective in reducing tunneling? Based on a sample of 966 listed companies that were listed before 2001 and the cumulative voting system was written into their articles of association，and using the panel data between 2002 and 2010，the differences between before and after the cumulative voting system was written into the articles of association are tested． The empirical results show that after the cumulative voting system has been written into the articles of association，tunneling decreased significantly． However，this governance effect is strongest in companies with controlling shareholder stake of less than 30%，and is significantly weakened in companies with controlling shareholder stake of more than 50%． The governance effect of the cumulative voting system in non-state-owned listed companies is stronger than in state-owned listed companies． After the government provided direct governance reform measures to reduce tunneling，the governance effect of the cumulative voting system weakened． The results show that the mandatory requirement for a stake of 30% as the cutoff point in the“Corporate Governance Guidelines for Listed Companies”did not achieve the desired results．With the introduction of direct governance reform measures to reduce tunneling，the mandatory provision of the cumulative voting system does not work anymore under the current background．