The 'Black and Yellow hitmaker proposed to Rose last year, months before announcing they were expecting their first child, reported TMZ online.
The couple had initially planned to wed in time for Christmas, but decided to postpone its plans until after the birth of their baby boy.
Khalifa and Rose welcomed little Sebastian in February this year and now the stars are preparing to become husband and wife in the coming months.
The licence is valid for 90 days and Khalifa reveals they are aiming for a wedding this autumn, once Rose regains her pre-pregnancy figure.
The pair began dating in 2010, following Rose's split from fellow new parent, Kanye West.