Ruwet was born in Saive in Belgium and studied philology in Liège. Later he studied with Claude Lévi-Strauss and later still with Noam Chomsky and Roman Jakobson at the Massachusetts Institute of Technology. He studied music privately.
Ruwet is best known for his work as a linguist and critic, but was also a significant figure in musical analysis. He attempted to make his analyses completely objective by not making any a priori assumptions about how the music worked, instead breaking the piece down into small parts and seeing how those parts related to each other, thus discovering the syntax of the piece without reference to any external sources or norms. His work in this field constitutes a kind of musical semiology.
Some of his musical analyses were published along with other works in Langage, musique, poésie (1972).