Is the benefits of Basic Old-Age Social Insurance received from China taxable in Canada?

You would need to check the tax treaty between Canada & China to see if your pension income would be taxable in China. You can see the treaty on the Canada.ca website: Agreement Between the Government of Canada and the Government of the People's Republic of China

There is a separate one with Hong Kong: Agreement Between The Government Of Canada And The Government Of The Hong Kong Special Administrative Region Of The People’s Republic Of China

You can also contact the Canada Revenue Agency (CRA) and ask them. If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency