Alcaraz, 18, beat Cilic, 33, 6-4, 6-4 in one hour and 35 minutes of play.
The Spaniard, number 16 in the ATP ranking, was again ruthless against the Croatian (23rd) and did not give up his serve even once during the game.
The new jewel of Spanish tennis will face the winner of the cross between the Greek Stefanos Tsitsipas, one of the candidates for the title, and the Australian Alex de Minaur in the first round of 16 in Miami.
Alcaraz broke into the tennis elite last year with a dazzling victory precisely against Tsitsipas at the US Open, when the Greek was number three in the world ranking.
This year, the Spaniard is experiencing a fabulous start to the season with 14 wins and only two losses, the last of them in a hectic semifinal of the Indian Wells Masters 1000 in which he put his idol Rafael Nadal on the ropes.
The entrance Alcaraz, jewel of Spanish tennis, dispatches Cilic and steps into the second round of the Miami Open was first published in diary TODAY.
