Brian Lightman, headteacher of St Cyres School, Penarth, has been named as the union council's preferred choice for the top job, taking over from John Dunford when he steps down next year.
Mr Lightman, who was ASCL president in 200708, will take control of the 14,000-strong union in September unless an election is triggered by another member.
His experience of being a school leader in both England and Wales has been welcomed by colleagues for its potential to bring a fresh perspective.
Mr Lightman, who was educated at a London comprehensive, rose to the post of deputy head of an Essex comprehensive before becoming headteacher of two schools in south Wales.
As head of St Cyres, he was one of the first to pilot the Assembly government's skills-led Welsh Baccalaureate, which he has since championed as the post-16 qualification of choice for the future.
His pioneering approach to the Bac was recognised by Jane Hutt, the education minister, who praised St Cyres as a "flagship" school in the development of the qualification.
As president of ASCL Mr Lightman fought to raise the status of school leaders and lobbied the Westminster and Assembly governments to improve school funding, change the inspections system and improve relations between institutions.
Gareth Jones, secretary of ASCL Cymru, said he was pleased for his colleague.
"He has gained the first step on what is a long journey," he said.
"If eventually he is successful he will be a very strong general secretary and I wish him well."
John Morgan, ASCL president and head of Conyers School in Yarm, Stockton- on-Tees, said: "Brian is an excellent headteacher and was an outstanding president of the association.
"His passion for education and learning, coupled with his long-standing commitment to ASCL and supporting our members, make him an ideal person to lead the association."
John Dunford, the outgoing general secretary, will have held the position for 11 years by the time he steps down.
He is courted by government ministers keen to get his members on side and has developed a reputation as a consummate networker and media-savvy operator.
Jane Lees, last year's ASCL president and head of Hindley High School in Wigan, said: "John Dunford is a hard act to follow, but times and people move on and we now have a younger group of leaders looking to the top to get them through."
Dr Dunford has rightly focused on improving the association's communications and has become a "statesman", Ms Lees said. "Brian is coming in at a different time, with different priorities with more emphasis on members," she added.
Sue Kirkham, another past president of the union and retired head of Walton High School in Stafford, said: "Brian is an excellent colleague, very personable and lively with a great sense of humour, but also extremely hard working.
"Having worked in England and Wales, he sees things from a different perspective, which will be a real benefit."
Mr Lightman was selected as ASCL's preferred candidate after an open application process. Any members wanting to oppose his appointment will have to do so by January 7, although it is believed this is unlikely.
Whoever takes over the job will have their challenges to deal with. Following a general election expected in May, whichever party wins will be facing severe pressure on public spending in an attempt to rein in public debt.
Mick Brookes, general secretary of the National Association of Head Teachers, which represents 28,000 school leaders, is also stepping down next year.
Both unions are part of the social partnership with government, which gives them a say on policy affecting teachers' working conditions. The Tories have already indicated that the influence of the partnership will be curtailed if they win power.