The transaction, which is pitched at 58p per share, requires Chinese regulatory approval, which is not expected by Huntsworth to go through until around October this year.
Huntsworth chief executive Lord Chadlington said: 'This relationship will help Huntsworth to achieve further growth and the investment will also significantly reduce our debt and therefore enable further investment in the engines of our growth in the coming years.'
The UK-listed group made the announcement alongside its financial results for the year ended 31 December 2012, which showed pre-tax profits rose 17.4% to £22.5m.
However, revenues failed to improve, falling 0.3% on a like-for-like basis to £173m.
Net debt was down 5.9% from 31 December 2011 to £66.9m as at 31 December 2012. Huntsworth stated it was comfortably within the terms of its £110m banking facilities, which are scheduled to reduce to £95m by 2015.
Oscar Zhao, the chief executive of BlueFocus, which Huntsworth claimed is Asia’s largest PR group, will join the Huntsworth board.
The two companies have also struck a strategic alliance focusing on four key areas: exchange of clients, exchange of skills, exchange of people and joint expansion into new markets.
BlueFocus was established in 1996 and has 29 offices, of which 24 are on the Chinese mainland.
It made revenues in 2012 of RMB 2.2bn (£233m), serves nearly 900 clients and employs around 2,000 people.
While its revenues are slightly higher than Huntsworth’s, its value on the Chinese stockmarket is £1.63bn compared to Huntsworth’s £175m value on the UK stockmarket.
Chadlington denied claims Huntsworth had come close to acquiring BlueFocus in 2006.
He said he and Zhao had been friends for eight years and had explored many different ways of working together.
Chadlington said: 'We can now offer global support to Chinese companies through the international Huntsworth network and provide our clients with in-depth service in China using the largest available Chinese PR network.'
Oscar Zhao, chief executive and founder of BlueFocus, said: 'Huntsworth provides our Chinese clients with a global platform to expand. We believe that Huntsworth's unique mix of public relations, healthcare and digital communications will prove invaluable to many Chinese businesses. These are the first steps in establishing together a genuinely global public relations service.'
Huntsworth’s key businesses are international PR consultancy Grayling and healthcare agency Huntsworth Health. It also owns corporate specialist Citigate and UK agency The Red Consultancy.
Grayling, the largest part of the group, was hit by a 3.1% decline in like-for-like revenues to £83.5m.
Citigate fared worse in a difficult climate for city PR firms, suffering a 10.5% drop to £22.8m.
However, Huntsworth Health offset the gloom with a 6.8% rise to £52.9m and The Red Consultancy outpaced that, growing 11% to £13.9m.
The group had reported pre-tax profits of £19.1m on revenues of £176.3m for the year ended 30 December 2011.
As it went into the 2012 financial year it took action to reduce its costs, having suffered a scare with the cancellation of £4m of client projects in Q4 of 2011.
In February this year it hired Edelman global technology practice chair Pete Pedersen as global chief executive of Grayling.