Mnemonics don't translate well and retaining their mnemonic nature. However, that isn't a critical issue.
For example, the common ctrl(or command) + X, C, V, A, W, Q are the standard shortcut in many languages even when they have no associated mnemonic. Even in English many common shortcuts have no mnemonic link.
Consistency is significantly more important than having mnemonics for key combinations. Changing key combinations between languages to suit the best mnemonics is likely to confuse users that work in more than one language, and possibly break with already established norms.
I would typically choose English as the base language for choosing shortcuts and mnemonics, as most existing norms are based on English. Additionally, I would stick to existing norms whenever possible, as this will lower the learning curve for users, and make your app feel more intuitive. However, if your application is going to predominate in China, and you are performing actions for which there are no common combinations already, I would do what works best in Chinese.
Edit: to clarify some confusion here, I am not saying that shortcuts are mnemonics, however mnemonics are related to shortcuts. For example, if the action were 'Copy' and the shortcut where
ctrl + c, then the mnemonic would be emphasising (usually underlining) the C in copy. But these are only mnemonics if there is a link between them. If the action for 'next article' is
y (as it is in Gmail), there really isn't any simple mnemonic linking 'y' and 'next article', and so there is no real mental relation between the action and the shortcut other than memorising it.