In 1992 Xi left Animal World and followed the Yunnan golden monkey research team, a three-year project by the World Wide Fund for Nature deep into the Baima Snow Mountain National Nature Reserve to shoot golden snub-nosed monkeys.

After three years of hard work he filmed the documentary Mystery Yunnan Snub-Nosed Monkey. These hauntingly beautiful primates, gentler than others of their kind and elfin-like, seem at once childlike and wise beyond their years.

It was the first time that humans had recorded the activities of Yunnan snub-nosed monkeys with a camera. The documentary is not only of important academic value, but has been praised for its artistic value and was later used as teaching material for environmental education in college classes. The film won the TVE award at the prestigious Wildscreen Festival in Bristol, England, in 2002.

After gaining fame with the film, Xi, started working on another documentary, Mystery Monkeys of Shangri-La, in 2012. It depicts a monkey family led by a formidable elderly leader that protects its eight or 10 clans against the hardships in the Himalayas using defensive strategies, collaboration and interdependence to survive. The film received an Emmy nomination for Outstanding Nature Programming in 2016.

Xi was born in Dali, Yunnan, a place close to nature, where wolves' howl can be heard at night. He thought that the world should be like what he witnessed in childhood.