The 46-year-old actor plans to hand the petition to the Pakistan government in a bid to free Sarabjit, who has been on death row in a Lahore jail since 1990.
"For over 20 years, Sarabjit Singh is in a Pakistan prison for a crime he did not commit. He and his family have suffered for too long. Please sign this petition to appeal to the Pakistan government that he be freed and united with his family in Punjab," Salman posted on his charity foundation Being Human's website.
The "Dabangg" star has previously said how he felt sad about Sarabjit's family and longed to launch his support for his release.
"Wanted to tweet this for the longest time, saw a picture of Sarabjit's sister, it killed me. Felt real sad for her. Help me help her. It's a personal request to all of you in Pakistan to send Sarabjit back to his family in Punjab, hope you find it in your hearts to help," he said.