How to apply for a China visa, I'm afghanistan?

You are not allowed to visit China in a self-service tour. You need to join a tour group organized by a Chinese travel agency authorized by the Ministry of Foreign Affairs of China. You need to submit the following requirements in person to China embassy in Afghanistan to obtain a China visa: your valid passport and a photocopy of the front, back and validity page of the passport, visa application form, one recent passport, covering letter from your company or office, original and photocopy of Invitation Letter issued by a Chinese travel agency authorized by the Ministry of Foreign Affairs of China, itinerary and name list of the tour group, other deemed necessary docements by the embassy.