Ryan, who earned four England caps and represented Saracens, Wasps, Newcastle and Bristol during his playing days, will act as interim forwards coach under the interim head coach Scott Johnson.
SRU chief executive Mark Dodson said: "Dean will be with us for 12 weeks and will bring all his top-flight coaching savvy and experience to benefit our forward pack."
And the 46-year-old Ryan added: "I've responded to an invitation from Scott to assist the Scotland management team over the next 12 weeks and will look to bring my experience to bear and give Scotland players the best opportunity to represent their country in the best way."
Former Scotland hooker Stevie Scott has also joined Johnson's team and the 39-year-old, who was a member of the management group which led Scotland A to a 35-0 victory over England Saxons last year, will work as an interim skills coach.
Ryan and Scott will work alongside Johnson, defence coach Matt Taylor, kicking coach Duncan Hodge and scrum coach Massimo Cuttitta.
And Dodson added: "Dean and Stevie will start work on Monday. I believe that, in Dean and Stevie, we have a combination of hard-nosed experience and deep-rooted understanding of Scottish rugby and its players, which Scott Johnson and his management team will be able to call upon."
Johnson said: "I'm delighted we have secured the services of Dean and Stevie for this year's Championship.
"To get people of their calibre in mid-season is a real coup. Dean is a sound, knowledgeable, mature rugby man and Stevie, with his background of having played 11 times for Scotland, knows what it means to wear the jersey.
"With Matt, Hodgey and Massimo already fully engaged in Six Nations planning, we've now got a management team in place for the start of the Championship next month."
Scotland will begin their 6 Nations campaign on 2 February, when they will take on England at Twickenham.
Scotland A post for Murray
Scotland's most-capped forward, Scott Murray, who won 87 caps between 1997 and 2007, is to assist the Scotland A head coach Shade Munro.
The 36-year-old Murray has been coaching the forwards, as well as playing for Mont de Marsan in the French top 14.
"I see this as a golden opportunity and anything I can give back to Scottish rugby, I'll be honoured to do," he said.
Source : http://www1.skysports.com/rugby-union/news/12505/8379825/Dean-Ryan-will-join-interim-Scotland-head-coach-Scott-Johnson-s-management-team
