I am an academic researcher i have been invited to deliver a lecturer in a university in Hong Kong.

Yes, you need a visa for this trip. You can apply for L or F type. You should first prepare a filled-out application form affixed with 1 passport-style photo, your passport and its photocopy, your introduction letter, round trip air tickets and hotel reservation and an invitation letter, bank statement. Next, go to the embassy of China to submit the application.