How do I take the train from Nanning to Haikou ? What is the time and fare ?

As there is no direct train service for this journey, I'm afraid u have to transfer on the way. I suggest you take a train to Yulin first and then transfer to another train to Haikou. The whole train duration takes around 11h.

Train from Nanning to Yulin costs CNY41.5 for a hard seat and the train to Haikou costs CNY92 for a hard seat, CNY174-190 for a hard sleeper and CNY272-284 for a soft sleeper. For the schedule, you can search at the train page of this website.

By the way, you can also consider taking a direct plane to travel and it only takes around an hour.