The world number two did not lose serve and broke Tien four times as he crushed the 19-year-old American 6-2, 6-2 at the ATP 500 event.
Sinner crushed 22 winners and saved two break points to claim his second crown in three years at the Beijing tournament.
It was the 24th edition of the ATP tournament in the Chinese capital, and there was no shortage of drama at the National Tennis Centre, with three players forced to retire mid-match from the quarter-finals onwards.
For lifting the trophy in Beijing, Sinner secured $751,075 in prize money, an increase on the $695,750 Carlos Alcaraz won for beating the Italian in the final at the 2024 event.
Tien was awarded $404,105 for his runner-up effort as he reached his first-ever final on the ATP Tour.
Sinner's triumph at the China Open has earned him 500 ATP Ranking points, which increases his points tally by 170 after he lost in the final last year.