Wang explains that an iPhone feature called 'Frequent Locations' can record locations users have visited frequently and the exact times of the visits.
Engineers warn that even if users choose to disable this feature the phone continues to record their locations, which is an information security risk.
Apple's iphone products are very popular in China, especially among the young people.
China is home to the world's biggest population at 1.3 billion, and it's an important revenue stream for Apple.