Can I apply for Chinese visa in Ulan bator

Prarik, it's possible that you can apply from there. What you need to prepare in advance are your passport and its copy, a filled application form, a passport style photo, the original and photocopy of your entry permit for Mongolia, round-trip tickets and hotel reservations, and other documents required by the embassy. After all the documents are collected, go to the consular office to apply for the L type.