Smith is returning to New Zealand to become part of Graham Henry'sAll Black coaching team with Wales coach Steve Hansen.
Solomons will bring with him forwards coach Adrian Kennedy whenhis three-year spell with Ulster ends at the end of May.
The 54-year-old former defence lawyer from Cape Town arrived inthe province when Ulster were in the doldrums but in a short space oftime he turned around their fortunes.
The former Springbok assistant coach guided Ulster to inauguralCeltic Cup success in December and they currently lead the Celtic League.
"There has been much speculation concerning Wayne's future atthe club and
Smith said: "This is a special club with extraordinary fansand a great group of players. I will never forget my time here. My accepting this new rolein no way undervalues how much Saints means to me.
"However, I love the All Blacks. I have been striving to playfor them or coach them for a large part of my life. They have asked me to go back and the fact is I cannotcontribute from here.
"I have a good relationship with Graham Henry and SteveHansen. The prospect of working together for New Zealand rugby excites me."