In his first interview since the earthquake, President Preval told and American newspaper he feared thousands of his people had died.
He called the scene in the capital "unimaginable", and said: "Parliament has collapsed. The tax office has collapsed. Schools have collapsed. Hospitals have collapsed."
It's the worst quake to hit Haiti in 200 years and has been described by one official there as a "catastrophe".
The centre of the quake hit near Port-au-Prince and was quickly followed by two strong aftershocks of 5.9 and 5.5 on the Richter scale.
Haiti is one of the world's poorest countries. The cost of the damage is already being estimated at billions of pounds.
American president Barack Obama said his thoughts were with everyone who'd been affected and that America was ready to help.
Elsewhere, rescue workers from around the world, including fire crews from Greater Manchester and Lancashire, travelled to Haiti on Wednesday to help with the search for survivors.