The Saudis drew 0-0 with Uzbekistan in their final Group A match on Tuesday to finish third behind the Uzbeks and Kuwait.
Oman, who finished third in Group D, had a superior goal difference than the Saudis to book their place in the finals.
The best third-placed team is decided by points and then goal difference. For the groups with six teams, such as Group D, the result against the bottom side is discounted.
In this case, Oman’s 2-0 victory over Turkmenistan is invalid, which gives them seven points from four games and a goal difference of +3 from a 6-3 tally.
The Saudis were in five-team Group A so there were no points deductions. But though they also gained seven points, their for-and-against record of 3-1 for a goal difference of +2 was one goal shy of Oman’s.
Uzbekistan topped the group with 10 points while Kuwait finished second after beating bottom side Afghanistan 6-0, with Mohammad Al Fahadi scoring four times and Mohammad Al Sarheed and Soud Al Enezi grabbing one each.
The top two teams in Groups A-G along with the best third-placed team join the Group H winners in the finals.
The final list of 16 qualifiers is as follows.
Group A
Uzbekistan
Kuwait
Group B
Iran
Tajikistan
Group C
Syria
Iraq
Group D
United Arab Emirates
Jordan
Group E
Japan
Indonesia
Group F
China
Timor Leste
Group G
DPR Korea
Vietnam
Group H
Australia
Best third-placed team
Oman (Group D)