secret ballot
noun [ C or U ] uk/ˌsiː.krət ˈbæl.ət/ us/ˌsiː.krət ˈbæl.ət/
无记名投票
a method of voting in which each person writes their choice on a piece of paper so that no one else knows how they have voted
The election of the new members is done by secret ballot. 新成员选举采取了无记名投票的方式。