How can i get China visa with Hong kong Visa

With the visa notice and invitation letter, you can submit your applications both to Chinese mainland and Hong Kong to Chinese embassy in Bangladesh. Other documents needed are your passport, copy of its personal information page, application forms for HK and Mianland China, Photos, return tickets and hotel reservation from China.
The regular processing time is 4 working days for Chinese mainland visa. But it may takes about one month if your application will be send to HK immigration department for approval.

Dear Concern,
Glad to receive your reply but could you inform me that i will stay in Hong kong only 2 days that is the reason will visa do also My friend told me that if i go for 5 days then visa does not need is it true ? can i enter in Hong kong with port entry ? Also inform me that need visa then how can i have the visa with urgent basis ? Please inform me .

Being Bangladeshi passport holder, you have to apply for a Hk visa for any purpose to HK including a short transit at the airport. You can use the express service by paying additional fees to the embassy when submitting the application if you are in a hurry.