We plan to attend China International Medical Equipment Fair in Shenzhen this Apr.we need visa?

You have to apply for a China Business visa from the China Embassy or consulate in your place of domicile. The documents required are:
1. your passport with blank pages and over 6 months validity and copy of the personal information page.
2. a completely filled visa application from.
3. Invitation Letter of Duly Authorized Unit or Confirmation Letter of Invitation.
4. Previously used China visa in old or new passport (Only visa stickers will be
accepted.
If it's your first time to China, you also need the folowings:
1. Original NBI clearance valid for travel abroad
2. Employment certificate, company ID, SSS ID and contributions, TIN ID and latest ITR