Nowadays, smart phones have become an indispensable tool in people's lives, more and used to deal with personal data as well as business data. Under this trend, the privacy of user data becomes the focus of concern. In order to protect the privacy of users, many mobile phone manufacturers provided corresponding security protection measures on the devices they produced. But in some special cases, the security measures provided by mobile phone manufacturers will not work, for example, when a user is held hostage or a user uses a mobile phone to collect evidence in a dangerous situation, the holder will forcibly check the user's mobile phone. At this time, the original protection measures of the equipment will be invalid. We designed a new hidden technology based on Android, which realizes data hiding storage by customizing and extending the Android mobile phone system ROM, and after the data is generated, calls the corresponding encryption module to encrypt the generated photos, audio, video and other files.