A composite product testing system including a main management system, a test equipment and a burn-in apparatus is disclosed. The test equipment and the burn-in apparatus are both arranged in a burn-in chamber of the testing system. First, multiple tested products are respectively inserted in multiple gauges of the burn-in chamber, and a burn-in procedure is activated for providing an aging environment. The main management system controls one of the gauges to connect with the test equipment for the test equipment to perform testing on the tested product upon the connected gauge. After the testing is completed, the main management system then controls the gauge to disconnect from the test equipment and re-connect with the burn-in apparatus, so as to monitor the tested product upon the gauge during the burn-in procedure.