As I know, Chinese embassy or consulates in the world have stopped to issue Chinese visa to Nigerians, for the requirements for Business Visa:
1. Qualified original invitation letter from the relevant Chinese Authorized Unit;

2. Qualified original invitation & guarantee letter with signature and stamp from the applicant's sponsor and business partner in China. The letter should state clearly applicant's name, position and passport number, applicant's company name, address and telephone number, purpose of visit, duration of stay and specific itinerary in China;

3. Qualified original introduction letter with the full name, title, date & signature of the issuing person from applicant's company. The letter should state clearly applicant's name, present occupation and position in the company, purpose of the visit, intended duration of stay, city intended to visit, name and address of applicant's business partner in China, items and quantity of goods planned to order and purchase;

4. Original Certificate of Incorporation;

5. Any proof of business connection with the inviting company in China (e.g. fax of business negotiation, contract, agreement, quotations of goods, invoices, bill of lading, etc.)

6. Applicant's passport copy--------Bio-data pages