The union has said it's confident the High Court will find "substantial" compensation and damages are due for what was a "black market" in "destroying workers reputations and job prospects".
It also said the initial claims are "the tip of the iceberg" and that there are some 3,000 other workers with claims.
Blacklisting was revealed in 2009 by the Information Commissioner's Office.
The ICO seized a database then, of 3,213 names of construction workers and environmental activists used by 44 companies.
The blacklist was drawn up by the Consulting Association, which has since been closed down.
Over 60% of those on the blacklist were aged between 30 and 50 in the mid-1990s. They were mainly active trade union lay leaders on construction sites. Many of them are now nearing retirement age with no pension arrangements, claims GMB.
Maria Ludkin, GMB national officer for legal and corporate affairs, said: "GMB is pleased to be the first union to bring this wide ranging High Court action on behalf of our members.
"Finally construction companies will be called to account for their systematic campaign to wipe out union organisation on construction sites."
The GMB has said this is the first High Court case taken by a trade union against "all the players in this conspiracy" and confirmed there will be further cases added to the 70.
Michael Newman, from law firm Leigh Day, which is involved in the legal case, said: "We are absolutely confident the High Court will find that substantial compensation and damages are due from the construction industry.
"Not only was this database hidden, but much of the information on it was irrelevant or just plain wrong. This didn't stop companies from trying to profit from blacklisting though, by keeping union workers off projects so they could meet project deadlines, regardless of concerns about health and safety, or working conditions."
He added: "Workers are only now finding out about this scandalous practice, and are rightly outraged."
