Tibet is a 13,000 foot high plateau overlooking the rest of Asia, with Indochina, India to the south and China to the east and north. Just as major rivers have their sources in Tibet, any attack on China to the east and north would be a downhill operation. A basic tenet of military strategy is to always hold the high ground. For this reason alone, the Chinese would want to control Tibet, so as to secure China's western flank.More: https://www.quora.com/Why-does-China-want-Tibet
