The capital gains tax in the mainland market of China is to suspend the increase of income, while there is no capital gains tax in the mainland market of China and Hongkong. Dividends are subject to a part of tax, which is called dividend tax. According to the regulations of the CSRC, the dividend of Hong Kong Stock Connect will be subject to 20% tax deduction.
Hong Kong Stock Connect is a technical connection between Shanghai Stock Exchange and Hong Kong Stock Exchange. It can buy and sell Hong Kong stocks without opening an account in Hong Kong. It is one of the convenient ways to invest in Hong Kong stocks. However, Hong Kong Stock Connect can't buy all Hong Kong stocks, only some.