The British No 1 took the first set in 20 minutes with breaks in both the second and sixth games and then broke Voinea twice more in the second to win in less than 44 minutes.
Throughout Henman hit the ball with authority, but the most impressive thing was his serving. Last week, despite reaching the final of the European Community Championship in Antwerp, his service below par.
Today 67 per cent of his first serves were successful and Voinea, whose head went down very early against his opponent's crisp hitting, had no answer.
Henman now faces the Czech Petr Korda in the second round and should be confident of another success, having beaten Korda in the Australian Open 13 months ago. Henman, No 14 in the world, is now looking for a place in the top 10.
The defending champion, Goran Ivanisevic, relied on his powerful serve to beat Cedric Pioline 7-6, 7-6 and reach the quarter-finals . Ivanisevic served 22 aces as he took an hour and 37 minutes to overcome the unseeded Frenchman, ranked 27th in the world. Ivanisevic is seeking his second title of the year after winning the Croatian Indoors in Zagreb earlier this month.
The world No 5 seemed fully fit after pulling out of last week's Antwerp tournament with shoulder tendinitis.
Sergi Bruguera and Daniel Vacek also earned quarter-final places. Vacek, who defeated Bohdan Ulihrach 7-6, 6-3, now meets Ivanisevic. Bruguera advanced with a convincing 6-4, 6-0 victory against his fellow Spaniard Javier Sanchez