I think you should apply for a F business visa from the China embassy in Bangladesh with the following documents:
1. Valid passport (at least six months before expiration) with blank visa pages and copy of the first three pages;
2. TYPED Visa Application Form with one passport photo.
3. Original Visa Notice Form issued by authorized departments of Chinese Government.
4. Round-way air ticket and hotel booking.
meanwhile, you have to pprepare the visa fee which can be got on this page above.