#查询到github上面的一个 方法对我有效，你可以试试。
1, copy dumpdecrypted.dylib into /usr/lib. Make sure it has appropriate permissions so that user mobile can read and execute it
-rwxr-xr-x 1 root wheel 197528 Aug 14 16:22 dumpdecrypted.dylib
2, change user to mobile:
su mobile
3, change directory into somewhere that mobile can write to:
cd /var/mobile/Documents
4, execute the command with absolute paths:
DYLD_INSERT_LIBRARIES=/usr/lib/dumpdecrypted.dylib /var/containers/Bundle/Application/59CEB222-4C4D-4A34-BC0F-8D38B9E3853D/MyApp.app/MyApp
5, then, you’ll have the MyApp.decrypted file in the current directory
Tested on Pangu jailbroken iOS 9.3.3