Qatar is ending its labour sponsorship system that forces foreign workers to seek their employer's permission to change jobs or leave the country.
It says a new contract-based law will replace the "kafala" system, ensuring greater flexibility and protection.
Human rights groups say the change leaves the system - which they describe as modern-day slavery - intact.
Qatar has imported hundreds of thousands of construction workers for the 2022 football World Cup.
Rights groups say many of them have died because of appalling working conditions.
Forced labour accusation
Qatar says a new law is coming into effect on Tuesday.
"These new legislative changes, combined with ongoing enforcement and a commitment to systemic reform, not just in Qatar but also in countries of origin, will ensure workers' rights are respected across the entire labour pathway," the government said in a statement.
But Amnesty International says the measure will not lead to significant changes.
"This new law may get rid of the word 'sponsorship' but it leaves the same basic system intact," Amnesty's James Lynch said.
Rights groups say that migrant workers will still need employer's consent to return home.
Earlier this year, Amnesty accused Qatar of using forced labour to prepare for the 2022 World Cup.
Qatar said it was "concerned" by the allegations and would investigate.