St Helens won the match 28-16 after a topsy-turvy game, ahead by 10 points at half time, then went 12-10 before roaring back to win by a clear margin.
St Helens started by thrashing National League Two side London Skolars 56-0.
In Round 5 St Helens narrowly beat fellow Super League side Warrington Wolves by 40–34.
In the quarter finals, St Helens again recorded narrow victory against Hull KR, winning by 24 points to 18.
Teams: St Helens: Paul Wellens, Ade Gardner, Matthew Gidley, Willie Talau, Francis Meli, Leon Pryce, Sean Long, Bryn Hargreaves, Keiron Cunningham, James Graham, Chris Flannery, Jon Wilkin, Paul Sculthorpe Replacements: James Roby, Lee Gilmour, Paul Clough, Maurie Fa'asavalu Coach: Daniel Anderson Hull: Todd Byrne, Matt Sing, Graeme Horne, Kirk Yeaman, Gareth Raynor, Danny Washbrook, Tommy Lee, Ewan Dowes, Shaun Berrigan, Peter Cusack, Willie Manu, Danny Tickle, Lee Radford (c), Replacements: Richard Horne, Garreth Carvell, Tom Briscoe, Jamie Thackray Coach: Richard Agar