I need to visit China for a conference in end of next month for 4 days. How i can get visa?

In general, you need to have a single entry F type for your meeting. You need to apply in your country's Chinese embassy.

The documents needs to prepare: your valid passport, an application form, a recent taken photo, Invitation Letter of Duly Authorized Unit or Confirmation Letter of Invitation, an invitation letter from your Chinese inviter, your company's covering letter and your bank statement.