Messi was the center of attention at the start of the game after his attempt to leave the club over the summer and Friday's criticism of the decision to sell Luis Suarez to Atletico Madrid, but Fati was the hero of the game, scoring in the 15th and 19th minute and then winning a penalty to allow Messi to add a third in a thrilling first half performance.
Sevilla came back from a goal down to get their season underway with a 3-1 win away to Cadiz.
More setbacks could well affect the entire season and increase the pressure on coach Lucien Favre at an early stage.
On the Beijing side, Shi Xiufeng and Ma Yina each contributed 14 points.
Elsewhere, Freiburg and Wolfsburg shared the spoils following a 1-1 stalemate as Josip Brekalo cancelled out Nils Petersen's opener. Enditem
Tourists can participate in a photo contest, enjoy traditional singing and dancing programs as well as discover Mongolian cuisine during the festival.
There was drama in the last minute of injury time when Robin le Normand had the ball in the Valencia net only for the VAR to rule it out for handball.
"I'm sure that the sports industry will play a more important role in the Chinese economy in the future." Enditem
In the 33rd minute Fati's acceleration then drew a foul in the area from Mario Gaspar and Messi slotted home the penalty to make it 3-0 and Pau Torres scored an own goal with the last action of the first half when he put Messi's clipped ball past the stranded Asenjo under timid pressure from Busquets.
Despite the loss, Shanghai is still secure atop the Suzhou division.
The use of new technology became a hot topic at the show, and more companies are trying to improve their products by using tech such as 5G and AI.