The Serie A side were keen to bring in a new defender after allowing Andrea Ranocchia to join Hull City on deadline day and have turned to Sainsbury to fill the void left by the Italy international.
Perth-born Sainsbury, 25, began his career in the A-League with the Central Coast Mariners and moved to China from Dutch club PEC Zwolle in January 2016.
But Sainsbury was deemed surplus to requirements at Jiangsu due to recent regulation changes only allowing CSL clubs to field just three foreign players, and they have now opted to send him to Inter for the remainder of the the current campaign.
Inter, who are owned by Suning Holdings Group along with Jiangsu, currently sit fourth on the Serie A table, nine points behind leaders Juventus.
25-year-old Sainsbury, who has won 24 caps for Australia after making his debut in September 2014, follows Atalanta's Roberto Gagliardini in joining Inter on loan in the January transfer window.