The Powergen Challenge Cup winners met fierce resistance from a Wildcats side fighting for survival but eventually saw them off with crucial second-half tries from Ade Gardner - who grabbed two - and Leon Pryce.
Wakefield had led early on through Jason Demetriou but paid the price for wasting a number of opportunities as Saints eventually wore them down.
With just two games remaining Saints are now effectively guaranteed the most favourable route to the Grand Final as only a mathematical miracle from Hull FC can prevent them finishing top.
Wakefield, 11th in the table, remain in deep trouble but they showed all the urgency that accompanies their position as they hit Saints hard from the start.
The Wildcats had gone into the game after winning two from three under new coach John Kear and their enterprising display showed again that they will not surrender meekly.
St Helens may still have been mentally celebrating last week�s cup final win as Wakefield dominated the opening quarter.
The Wildcats claimed the lead after just two minutes with a Jamie Rooney penalty following a break by Mark Atkins from a David Solomona offload.
Stand-off Rooney was relishing the challenge and a try followed just four minutes later as his kick cut Saints open and James Evans and Ben Jeffries combined well to put Demetriou over.
Rooney missed the conversion and Wakefield spurned two more chances to extend their lead as Kevin Henderson knocked on and Demetriou failed to gather a well-flighted kick from his stand-off.
Saints were struggling to shake off their post-Twickenham lethargy and their best chance of the early stages broke down when James Graham was intercepted by Atkins.
The hosts also suffered the loss of prop Nick Fozzard, who was carried off on a stretcher with a serious-looking injury after a five-minute stoppage.
Yet Saints weathered the storm and got back into the game with a flash of brilliance that saw Keiron Cunningham and Jamie Lyon combine to put Paul Wellens over.
Lyon levelled the scores with the conversion and, despite a lack of Saints urgency, then put them ahead with a try under the posts following good work by Sean Long and Paul Anderson.
He added his second goal before Lee Gilmour crashed over to put Saints 16-6 ahead at half-time.
Wakefield failed to take advantage of yet another opportunity early in the second half after Solomona set Semi Tadulala free with an astute pass.
Tadulala looked to have the beating of the defence but waited for support and the chance was lost as Jeffries dropped the ball.
Yet the Wildcats managed to maintain their intensity and their persistence was rewarded as Mark Field drove to the line and Adam Watene barged over.
Rooney�s conversion brought the score back to 16-12 but, typically, Saints had more when it mattered.
Long, fresh from winning the Lance Todd Trophy for a record third time, created a fourth Saints try with a high kick to the corner for Gardner.
Lyon, who like team-mate Jon Wilkin at Twickenham last week, finished the game with a bandage around his face and could have suffered further injury when he was head-butted by Michael Korkidas.
Korkidas committed his offence right in front of the touch judge and referee Karl Kirkpatrick immediately sent him off.
Saints took advantage of their extra man as Leon Pryce added another try from dummy half and Lyon converted.
He added another penalty soon afterwards, before Gardner claimed his second try in the last minute and Jason Hooper converted.
St Helens: Wellens, Gardner, Lyon, Gilmour, Meli, Pryce, Long, Fozzard, Cunningham, P Anderson, Sculthorpe, V. Anderson, Hooper. Replacements: Roby, Graham, Fa'asavalu, Bennett.
Wakefield Trinity Wildcats: Halpenny, Demetriou, Evans, Atkins, Tadulala, Rooney, Jeffries, Korkidas, Obst, Watene, Henderson, Solomona, Betham. Replacements: M. Field, Elima, Latu, March.
St Helens: (16) 34. Tries: Wellens, Lyon, Gilmour, Gardner 2, Pryce. Goals: Lyon 4, Hooper.
Wakefield Trinity Wildcats: (6) 12. Tries: Demetriou, Watene. Goals: Rooney 2.
Referee: K Kirkpatrick