In other games on Sunday Australia defeated China 4-1 and Japan beat Uzbekistan 5-3.
The UAE beat Bahrain 4-1 in a friendly exhibition match.
The Iranians scored their first goal in the opening seconds of the game when Moslem Mesigar found the back of the net. Mesigar then added another in the second minute to give Iran a 2-0 lead.
Oman hit back in the second period scoring two goals to equalise before Iran again wrapped up the second period 4-2.
Mesigar sealed the win with his third, scoring in the eighth minute to put Iran through to the semifinal stage.
"I think is shows that this is very strong team and as the head coach of the Australian team said yesterday, they were born to play in the sand," said Iranian coach Resa Sadegh Pour.
"Beach soccer is in their blood and I think for the next match they will become better and we will qualify for the World Cup."
Earlier in the afternoon Australia recorded their first win in an international beach soccer match, defeating China 4-1 on pitch three in the second round of the group stage.
The win means Australia occupy second place in Group B and are ahead of Oman on goal difference.
Australia took the lead, scoring in the first minute when Michael Matricciani found the back of the net. He then scored his second in the fifth minute of the first period.
At the end of the second, Australia had extended its lead to 3-0, when Demetrios Bakis scored his first goal of the tournament.
The Australians extended their lead to 4-0 with Matricciani scoring his third goal. The only Chinese goal was scored in the final two minutes of the match.
Australia entered this tournament with no experience and had pulled the team together in a matter of weeks.
Australia faces Oman today in a crucial game to decide which of the teams will grab second place in the group.
The Fifa Beach Soccer World Cup 2009 Qualifier Dubai is the tournament that qualifies Asia's representatives for the Fifa Beach Soccer World Cup 2009 Dubai.
The seven participants were placed in two groups, one group of three and the second group of four teams. The group with the fewest teams will play a friendly match against either the UAE or France, to ensure all teams play an equal number of matches. The friendly match has no impact on the final result in the Group A.
Results
Iran 5 Oman 3
China 1 Australia 4
Japan 5 Uzbekistan 3
Bahrain 1 UAE 4
(Friendly match)
Today's matches:
14:45 Iran vs China
15:00 Oman vs Australia
16:00 Japan vs Bahrain
16:00 Uzbekistan vs France (Friendly match)