Please be noticed that Chinese Visa and Tibet Permit are two things totally different.
To enter Tibet, or any part of China excepting Hong Kong and Macao, a Chinese visa is necessary. You’d better obtain it before leaving your home country.

When applying for a visa as an independent traveler, your application might be rejected if you mention that you plan to visit Tibet. There is a trick that when you apply for the Chinese visa, you don’t need to tell the embassy officer that you have the plan for traveling to Tibet; instead you can inform them you want to travel to somewhere else of China such as Beijing, Shanghai, Chengdu etc. or else the application would become complicated and arduous.

Please Be Noticed
•When entering China you’d better have a visa covering the expected duration of stay. Getting extensions inside China can involve delays and other difficulties.
•You need to apply for a Two times or Multiple-entry visa when you need to leave and re-enter mainland China. Please be noticed that, even when you leave for Hong Kong or Macau from mainland China, you still need to have a Two times or Multiple-entry visa.

Tibet Permits (Tibet Visa) Categories
There are four levels of bureaucracy you need to jump through to travel in Tibet: a Chinese visa to entry China, a Tibet Tourism Bureau (TTB) permit or  the entry permit. Alien’s Travel Permit, If you travel to certain regions of Tibet, Military Permission and Frontier Permission are also required.  Beware that Tibet travel permit situation is subject to rapid and unpredictable change. Contact us directly to get the latest Tibet permit situation within 12 hours.
•TTB (Tibet Entry Permit)
•PSB (Alien’s Travel Permit)
•Military Permission

Please Be Noticed
•You have to tell us your real occupation as journalists and people who involved in political matters could be revoked (diplomats, journalists, and government officials who should travel to Tibet under the arrangement by the Foreign Affairs Office).
•Please note that if you do not book any tour from us, we can not help you get the permits. No travel agency could provide “permit-only” service. A must service includes vehicle and guide.
•After having a permit, we could buy you the air tickets, and you can pass the check-in at the airport and board the plane.
•Only the guide could hold the permit after you establish yourself on Tibet land. You are not allowed to bring with it and travel to anywhere you want.
•Generally speaking, it will cost us 3-5 working days to get the Tibet permit if you could supply the full necessary documents in time.