Chief Executive Carrie Lam on Sunday dismissed suggestions that the revamped electoral system is designed to screen out opposition voices.
She made the remarks as voting began for about a quarter of the 1,500 seats on the election committee.
Some 4,900 voters are eligible to cast their ballots at five polling stations across Hong Kong.
All candidates have passed a vetting process that ensures only those deemed to be patriots can hold public office.
The rest of the seats have already been decided – either because they're uncontested, appointed, or are ex-officio positions. Of 40 subsectors, competitive polls will be held for just 13.
The election committee will choose the SAR’s next chief executive and the largest grouping in the new Legislative Council.
Lam said the vetting mechanism is to safeguard national security and national interest.
“The whole objective of improving the electoral system of the Hong Kong Special Administrative Region is to ensure patriots administer Hong Kong. This is a very legitimate objective of any public election in any government,” she said.
“I doubt very much that another government or another country will allow the public elections to their local legislature to consist of people whose mission is to undermine the national interest or the national security,” said Lam.
"We still welcome people from all walks of life, people who have different opinion about the government policies, to go into the political system, as long as we all share the common objective that we will continue to succeed under One Country Two Systems and we will not do anything to undermine national security.”