Born in Le Bugue, in the Périgord (Dordogne département), he studied medicine at the University of Montpellier.
He practised medicine in his native town and corresponded with René Descartes and Marin Mersenne.
His discovery of the weight of air also made possible the invention of the barometer by Evangelista Torricelli in 1643.
He also developed a device called a "Thermoscope", a precursor of the thermometer.
Jean Rey died in Le Bugue, where he had lived all his life.