Terrence Trammell of the United States took silver, as he did at the 2000 Olympics and last year's world championships, in 13.18, with 2000 Olympic champion Anier Garcia of Cuba third in 13.20.
Liu's personal best going into the race was 13.06.
Liu matched the mark set 11 years ago by Briton Colin Jackson in Stuttgart, Germany.
He led almost from the start and while others floundered the Chinese maintained his rhythm and screamed in delighted disbelief as he flashed over the line.