Zhuānxīn ɡōnɡzuò.
专心工作。
Keep your mind on your work.

 
Notes:
专心(zhuānxīn): keep mind on
工作(ɡōnɡzuò): work
 
Example:
A：你昨天去酒吧了吗？
     Nǐ zuótiān qù jiǔbɑ le mɑ？
     Did you go to bar yesterday?
B：专心工作。
     Zhuānxīn ɡōnɡzuò.
     Keep your mind on work.