Swindon's Ladies started on the front foot creating chances and took the lead when Kirsty Shell converted a good ball from Amy Baker making it 1-0 at half time.
Despite losing Michelle Rich through injury at the break, Swindon started brightly again creating more chances and Shell grabbed her second to make it 2-0.
Southampton did get one back making it 2-1 from their only chance in the game. Swindon kept creating chances and Southampton's goalkeeper worked hard to keep Town at bay.
The Ladies did score a third when Kirsty Shell was brought down for a penalty which Catherine Reid converted to make it 3-1.
Swindon are at home to Gloucester this Sunday at Fairford Town FC, with kick-off at 2pm.
