Southport's first came when Kevin Leadbetter played the ball to Carl Baker just outside the area. He controlled the ball and then shot fiercely to give the Sandgrounders an early advantage.
A minute later Southport extended their lead when Matty McGinn collected the ball on the left wing and passed across the face of the goal where Bakerwas waiting on the back post to slot beyond the stranded Ryan Clarke.
Forest Green were given few early chances with their first effort being a Paul Wanless free-kick which was on target but collected comfortably by Steve Dickinson.
Minutes later, however, they pulled a goal back when Southport gave away another free kick just outside the area.
It was taken by Jon Beswetherick and after it was parried by Dickinson the ball fell kindly for Jon Richardson who made no mistake from close range.
Southport regained their two-goal advantage in the 24th minute when Kevin Lynch played a ball to Kevin Leadbetter who released Steve Daly who beat the keeper in a one-on-one situation.
Leadbetter tried to get on the scoresheet when he dispossessed a Forest Green defender near the corner flag but his goalbound shot was parried around the post for a corner.
As the half time whistle approached Clarke did well to block Daly's close-range header from McGinn's free-kick.
Forest Green thought they had pulled a goal back early in the second half when they were awarded a free kick which was quickly taken but Bruno Teixeira had strayed offside.
Dickinson cleared the ball off his line moments later when Zema Abbey shot from close range following a corner.
Southport absorbed the early second half pressure and started to attack with Daly coming close with a header from a Baker corner.
Forest Green kept pushing and nearly closed the gap when Abbey played a ball to Jamie Gosling who in turn found Wanless but his shot was saved by Dickinson.
Matt Gadsby tried his luck when he spotted Dickinson off his line but a goalline clearance from Farrell Kilbane protected the Southport lead.