Abelardo Fernandez and Rafael Berges scored the semi-final goals in the Luis Casanova stadium which saw Spain, runners-up in the 1920 Olympics, through to Saturday's final in Barcelona.
Ghana were reduced to 10 men early in the second half when defender Osei Kuffuor was sent off for his second bookable offence.
Fernandez gave Spain the lead in the 26th minute after Kuffuor, of Torino, had fouled Jose Amavisca deep in the Ghana half.
Barcelona's Josep Guardiola took the kick out on the left flank and Fernandez, finding space in the box, stole in to stab home a shot between Kuffuor and Mohammed Kalilu.
The Ghana goalkeeper, Anthony Mensah, performed heroically to limit Spain to a one-goal lead before the interval. He turned a tremendous shot from Alberto Ferrer, the chunky Barcelona player, round his post in the 36th minute and saved from Amavisca three minutes later when the forward had the goal at his mercy.
Ghana's skilful players provided periods of danger for the Spanish defence, with Yaw Preko and Bernard Aryee raiding on the flanks. But Spain, the only team in the tournament with a 100 per cent record, have yet to concede a goal and proved equal to Ghana's unceasing efforts to try to turn the game round.
The match was a personal disaster for Kuffuor, who was booked in the third minute and then sent off two minutes after the interval for felling Luis Enrique.
Spain, with the advantage of an extra man, overran their African opponents and Berges rammed in their second goal from 20 yards in the 54th minute.
In the second semi-final at Barcelona's Nou Camp stadium, Andrzej Juskowiak scored a hat- trick as Poland thrashed Australia, who had beaten Denmark and Sweden en route to the last four.
Juskowiak, an astute new signing by Bobby Robson at Sporting Lisbon, ended Australia's dream run with two strikes in a nine- minute period either side of halftime and elevated himself to the role of leading tournament scorer with seven goals in six games.
His striking partner, Wojciech Kowalczyk, of Legia Warsaw, also grabbed two as Poland ran riot in the second half.
Spain will be favourites for gold - and enormous bonuses for their players - but Poland will not give up easily.Reuse content