In the match held at the Taipei Municipal Stadium in Taipei, Shabnam Behesht (29th and 62nd), Fereshteh Karimi (34th), Paria Norouzi (77th) and Fatemeh Arjangi (88th - penalty) were on target for the Iranian football team.
Phayvanh scored the only goal for Laos in the 33rd minute.
Iran has been scheduled to face Chinese Taipei on Tuesday.
The winners of Group C will join Myanmar and Jordan, who topped Groups A and B respectively, Thailand and Vietnam in Round 2 with a place in the final round going to the side that finishes top of the five-team table.
The top-two sides from the Qualification Final Round - which features reigning Asian champion Japan, 2014 AFC Asian Cup runner-up Australia, DPR Korea, China, and Korea Republic - will fly the Asian flag at the women’s football tournament of the 2016 Olympic Games in Rio.