Malawi’s High Court is expected to rule on Friday whether she should be granted an interim adoption of a four-year-old girl, Mercy James.
The government came under fire after Madonna adopted a 13-month-old Malawian child, David Banda, in 2006, with critics accusing it of giving her special treatment by skirting laws that ban non-residents from adopting children.
Malawian Information Minister Patricia Kaliati said Madonna had helped in the country and was a worthy mother.
"Madonna has been good to us, she is supporting over 25,000 orphans in this country and she has proved that she can take care of David," Kaliati told Reuters.
"Very few rich and famous people can take time to fly all the way to Malawi to support our children we support her adoption process."
An estimated 1 million children have been orphaned by AIDS in Malawi.
Malawian civil society groups oppose the adoption and a local human rights activist said it would amount to child trafficking.
"She is not skirting any legal issues in her application to adopt this child and is looking to provide a loving family environment and the best education and health care possible for a child who has been in an orphanage since her birth," spokeswoman Liz Rosenberg said in a statement sent to Reuters on Tuesday.
Madonna, accompanied by David, arrived in Malawi on Sunday ahead of the court examination of her application.
The star, who was divorced last year from British film director Guy Ritchie, is one of the most successful singers of all time, with album sales of more than 200 million.