Carlos Queiroz's side drew first blood after 18 minutes of a one-sided quarter-final when Azmoun squared for Taremi to sweep home after some calamitous Chinese defending. Iran's second was almost a carbon copy - much to the chagrin of China manager Marcello Lippi.
This time Liu Yiming misjudged a hopeful punt down-field, allowing Azmoun to nip in and round goalkeeper Yan Junling to score his fourth of the tournament.
China's best chance came after just six minutes when Hao Junmin wriggled free, only for Iran defender Ramin Rezaeian to slide in with a superb goal-line clearance to deny Wu Lei a tap-in.
Iran could have been out of sight by half time as Azmoun - known by Team Melli fans as the "Iranian Messi" - twice went close and Taremi missed an open goal.
Ehsan Hajsafi forced a sharp save from Yan on the hour mark before Ansarifard raced clear to add a third in stoppage time.