The 9-year-old sings on the track, called 'Whip My Hair', in which she repeats the chorus "I whip my hair back and forth".
The song has already clocked up over 70,000 views on YouTube since its leak, and has gained praise from fellow artists.
Solange Knowles recently tweeted: "Willow Smith make me wanna whip some haiiirrr in this house. Ummm kill em girl. Kill em!"
While Smith is currently unsigned, rumours suggest that she is to ink a deal with Jay-Z's Roc Nation label.
Willow, who is said to be inspired by Rihanna, is the youngest member of the Smith family. Her brother, 12-year-old Jaden, has starred in several films including The Pursuit Of Happyness and The Karate Kid.