By Joanne Chiu

Alibaba Group Holding Ltd. and other Chinese technology companies appear set to join Hong Kong's main stock benchmark, after the compilers of the city's flagship Hang Seng index revamped their inclusion rules.

The changes will permit shares with unequal voting rights or primary listings elsewhere to join the 50-year-old index, making Alibaba and others such as Xiaomi Corp. and Meituan Dianping eligible for entry.

The overhaul follows a campaign by Hong Kong Exchanges and Clearing Ltd., the operator of the city's stock exchange, in recent years to win listings from Chinese tech and biotechnology companies, partly by changing its stance on corporate governance.

Hang Seng Indexes Co. will implement its new rules when it next reviews the index in August, and any inclusions will take effect in September, said Daniel Wong, director and head of research and analytics, in a call with reporters. He declined to name potential candidates.

To start with, no new constituent will be able to make up more than 5% of the index, which now has 50 members. Mr. Wong said any future changes to this 5% ceiling would depend on market responses.

The changes apply only to companies from Greater China, and their weighting will depend on the value of their freely tradable stock in Hong Kong.

New York-listed Alibaba raised nearly $13 billion through a stock sale in Hong Kong in November. E-commerce competitor JD.com Inc. is likely to follow suit, after it filed a confidential application in April for a secondary listing in Hong Kong.

Smartphone-maker Xiaomi and Meituan Dianping, whose app offers services such as food delivery, both chose Hong Kong as their main listing venue but have been ineligible for the main Hang Seng index because both have super-voting shares. The prospect of inclusion in the main benchmark index could help attract more listings to Hong Kong.

The Hang Seng index is dominated by old-economy companies such as banks, insurers and real-estate developers. Some investors have said it could be more representative of China's changing economy as the country switches to high-value industries from low-end manufacturing. The index has dropped 15% this year, lagging U.S. benchmarks and the Shanghai Composite.

The index changes follow a public consultation, launched in January. Hang Seng Indexes said more than 90% of respondents supported the proposals, which will also affect its Hang Seng China Enterprises Index.

Write to Joanne Chiu at joanne.chiu@wsj.com