I am Yemenis Merchant What I need to get visa ?

Do you mean you are in Djibouti now? Chinese Embassy in Djibouti doesn't accept Chinese visa application by post. You should go to the embassy to submit your application in person or entrust a friend, trave/visa agent to do the application on your behalf. The documents required may be different from differen travel purpose. However, the basic documents for a Chinese visa application includes your original passport with at least 6 months validity and enough blank pages, completely filled visa applicationf form V2011A & V2011B (since you are applying visa in a third country rather than your home country) and two passport size photos.