The two largest cities in Guangdong have announced they want to cap their populations and prevent low-skilled migrants staying.
Those who do not have a 'rightful reason' to stay will be detained and sent back to their home provinces, the Deputy Mayor of Guangzhou, Zhang Guifang, said this week.
Mr Zhang did not specify what would be considered a 'rightful reason' to stay.
Shenzhen's new policy on obtaining a temporary residency permit will make it virtually impossible for migrants who do not have a job to stay.
Previously, migrant workers could apply for a temporary permit card for 300 yuan (HK$285) a year. Under the new regulations, permits must be sought through the applicant's employer, who must also provide proof that the employment follows the government hiring policies.
The new directive says companies should hire 40 to 50 per cent of their staff from among local, long-stay residents.
The Shenzhen policy changes will make it more difficult for workers from other provinces to find jobs in the city.