Hi, how to get to shenzhen railway station / luohu from shenzhen north? I'm going to HK. thanks?

As for the Shenzhen North, do you mean the Shenzhen North Railway Station?
If so, you can take the subway Longhua Line to from the Shenzhen North Railway Station to reach Convention and Exhibition Center and then change to Luobao Line to get to Luohu, where the Shenzhen Railway Station locates.