After graduation, Renier practiced medicine in Bologna, Florence, and Chioggia, where he held the position of health officer.

Renier authored important studies in zoology and marine biology, particularly on mollusks and shells of the Adriatic, topics on which he published a significant treatise.

Later, he was commissioned by the Austrian government to create three marine zoological collections for the universities of Bologna, Padua, and Pavia (F. Barbagli).

Part of his collection of marine animals was sold in 1818 to the Natural History Cabinet in Vienna.

Renier was also a member of Italian and international scientific academies and societies of the time, including the Venetian Institute of Sciences, Letters and Arts.