I stay in china have resident permit.my home country sri lanka

If you go there for sightseeing purposes, you need to apply for a tourist entry permit. First thing is to prepare the required documents containing copy of your passport, the application form, a bareheaded color photo, proof of your financial support, hotel booking record, transportation arrangement and your travel plan.
Next, submit the application to Beijing office of HK government to apply for HK tourist entry permit.