Visit Macau then China from Bangladesh. whats system for apply visa

You need to apply seperately for Macau and China through Chinese embassy in your country.

For applying the one to Macau, you need to hand in the Macau's application form, copy of your passport, flights tickets to Macau, financial documents such such as your bank statement, hotel reservation letter, proof of visit's purpose, travel documents affixed with Macao entry and exit stamps (if any) and valid entry permit to other countries or regions (if any).

For applying the single trip L type to China mainland, you need to provide the round trip tickets to China, your hotel booking in China, your passport, application form with recent taken photos for applying.

Hope you can get both of them in the end.