It is impossible to open an account directly in the mainland, and the through train for Hong Kong stocks has not yet been opened. If you want to buy, you can open an account with a business company established in the Mainland through a regular Hong Kong brokerage company. For example, KGI Securities and Hengfeng Securities in Hong Kong have branches or offices in the Mainland, which can help you open an account. The required documents include ID card, household registration book, real estate license and other documents. Almost all ordinary mainland citizens have the conditions to open an account.
In addition, China mainland securities companies have branches in Hong Kong. Companies that can trade Hong Kong stocks in the Mainland can also open accounts to speculate in Hong Kong stocks. Such as China Merchants Securities Hong Kong and Guotai Junan Hong Kong.